Best freeware

Applied fields

CAx
Main article: :Category:Free computer-aided design software

Electronic design automation (EDA)
Main article: :Category:Free EDA software

Finance
BulmaGes — Qt-based
GnuCash — Double-entry book-keeping
Grisbi — Single-entry
JCash — Java-based
jFin
JGnash — Java-based, double-entry book-keeping
JMoney — Java-based
KMyMoney — Double-entry book-keeping
LX-Office — Double-entry book-keeping/ german adaption(SQL-Ledger fork)
Marketcetera — Algorithmic trading platform for equities, options and more
Money Manager Ex personal finance organizer
Opentick — Market-data (U.S. Markets) source feed for software development
PayThyme — Payroll software
phpOrganisation
QuantLib — Quantitative finance libraries
Quasar Accounting
QuickFIX — FIX protocol engine written in C++ with interfaces for several languages
QuickFIX/J — FIX protocol engine written in Java
QuotesViewer — Euronext stock quotes, watchlist
SQL Ledger — Double-entry book-keeping
TimeTrex — Payroll and Time Management
TurboCASH — Double-entry book-keeping for Windows
LAMP Accounts — LAMP based day to day business management software
See also: Comparison of accounting software

Mathematics
Main article: :Category:Free mathematics software

Science
Main article: :Category:Free science software

Geographic information system
GRASS GIS
gvSIG
ILWIS(Integrated Land and Water Information System)
JTS Topology Suite
MapGuide Open Source
NASA World Wind — open-source virtual globe
Mapnik
OpenMap — Java based programmer's toolkit
Quantum GIS — Desktop GIS
TerraLib — GIS classes and functions library
uDig — User-friendly Desktop Internet GIS
OpenEV — an elevation viewer

Plotting
Main article: :Category:Free plotting software

Scanning probe microscopy
Gwyddion — Scientific data analysis
Gxsm — Gnome X Scanning Microscopy - dsp supported scanning probe acquisition

Microscope image processing
CellProfiler
ImageJ

Molecule viewer
Jmol
Molekel
PyMOL

Bioinformatics
Bioclipse

Cheminformatics
Chemistry Development Kit
JOELib
OpenBabel

Biological data management
BioRails

Statistics
Main article: :Category:Free statistical software

Assistive technology

Speech (Speech Synthesis, Speech Recognition)
Text2Speech — Lightweight and easy to use Text To Speech (TTS) Software
Emacspeak — Audio desktop
Festival Speech Synthesis System
CMU Sphinx — Speech recognition software from Carnegie Mellon University

Other Assistive Technology
Dasher — Unique text input software
Gnopernicus — AT suite for GNOME 2
PowerTalk — Automatic Text narration of presentations
pVoice — Application for Augmentative and Alternative Communication (AAC)
Virtual Magnifying Glass - a free, open source, multiplatform, screen magnification tool.

Data storage and management

Backup software
Main article: :Category:Free backup software
See also: List of backup software
Cobian Backup

File archivers
Main article: :Category:Free data compression software

Database management systems (including administration)
Main article: :Category:Open source database management systems

Data mining
Weka -- data mining software written in Java featuring machine learning operators for classification, regression, and clustering.
YALE -- data mining software written in Java, fully integrating Weka, featuring 350+ operators for preprocessing, machine learning, visualization, etc.
Scriptella ETL -- ETL (Extract-Transform-Load) and script execution tool. Supports integration with J2EE and Spring. Provides connectors to CSV, LDAP, XML, JDBC/ODBC and other data sources.

Enterprise search engines
Kneobase


DjVu
DjView

Educational

Educational Suites
ChildsPlay
GCompris
Docebo LMS
IUP Portfolio

Language
ForLatin
Kiten
KLettres
KMessedWords
KVerbos
KVocTrain

Typing
KTouch

Geography
KGeography

Other educational programs
Focus/SIS
KEduca
PSCafe POS



Genealogy
Main article: :Category:Free genealogy software

Graphical user interface

Media


Audio editors / audio management
Ardour (audio processor)
Audacity
BashPodder
CD-DA X-Tractor
CDex
Grip audio ripper
JACK Audio Connection Kit
Linux MultiMedia Studio
MusE
OpenSebJ
Pure Data
Rosegarden
Streamripper
SoX

Graphics
Main article: :Category:Free graphics software

Image galleries
Main article: :Category:Free image galleries

Image viewers
Eye of GNOME
F-spot
imgSeek
Imgv
JavaExplorer
Java Image Browser and Sorter
JImageView — Java-based
SlideShow Picture Viewer

Media players
Main article: :Category:Free media players

Radio
Dream DRM Receiver

Television
Main article: :Category:Free television software

2D animation
KToon
Synfig
Pencil - les stooges

Video editing
Avidemux
AviSynth
Cinelerra
DScaler
GNU VCDImager
Jahshaka
Kino
LiVES
Mpeg2Schnitt
VirtualDub
VirtualDubMod

CD-writing software
Main article: :Category:Free CD writing software

Other Media packages
Gnome Subtitles
Celtx - Media Pre-production Software

Networking and Internet
RSS/Atom readers/aggregators
RSS Bandit - Windows - .NET
RSSOwl - Windows, Mac OS X, Solaris, Linux - Java SWT Eclipse
Vienna - Mac OS X
Akregator - Platforms running KDE
Sage (Mozilla Firefox extension)

Communication-related
1videoConference — Open Source, P2P, Web2.0 and VoIP multipoint audio, video, text conferencing platform
Asterisk — Telephony and VoIP server
Ekiga — Video conferencing application for GNOME
FreePBX — Front-end and advanced PBX configuration for Asterisk
SIP Communicator— Java VoIP and Instant Messaging client
sipX — SIP Communications Server
Slrn — a newsreader
Speak Freely — Internet voice chat
Wengophone — Free Voice, Video and IM client application

Remote access And Management
FreeNX
GenControl — Based on VNC with GUI Interface.
rdesktop
Synergy
VNC (RealVNC, TightVNC, Ultr@VNC)
Purgos Windows Computer Management



Webcam
Dorgem
Fwink

Webgrabber
cURL
HTTrack
Wget

Web-related
BookmarkSync — a tool for browsers
Apache Cocoon — a web application framework
Apache — the most popular web server
AWStats — a log file parser and analyzer
HTTP File Server — a user friendly file server software with a drag and drop interface
lighttpd — Resource sparing but also fast and full featured HTTP Server
NetKernel — an internet application server
Squid cache — web proxy cache
Web-Developer Server Suite — a package of web applications including Apache, MySQL, and PHP
XAMPP — a package of web applications including Apache and MySQL
Zope — a web application server

Portal Server
Drupal
Joomla!
OpenPHPNuke
PHP-Nuke
PostNuke
uPortal
Textpattern

Middleware
Geronimo Application Server
GlassFish Application Server
Jakarta Tomcat — a servlet container and standalone webserver
JBoss Application Server an application server
ObjectWeb JOnAS — Java Open Application Server, a J2EE application server
SmartVariables — a generic network-shared object application server
JacORB — Java implementation of the OMG's CORBA standard
TAO (software) — C++ implementation of the OMG's CORBA standard

Other networking programs
OpenLDAP — an open source LDAP server
JXplorer — an open source LDAP client
openVXI — an open source VoiceXML interpreter
YaCy — P2P-based search engine

Operating systems
Be advised that available distributions of these systems can contain, or offer to build and install, added software that is neither free software nor open source.

Password management
Ked Password Manager
KeePass
Password Safe

Personal information managers
Chandler — In development by Mitch Kapor and the OSAF.
KAddressBook
KNotes
KonsoleKalendar
Kontact
KOrganizer
Mozilla Calendar — A Mozilla-based, multiplatform calendar program.
OpenSync (software)
Novell Evolution
Task Coach — Your friendly task manager.
TreeLine

Programming language support
ArgoUML — ArgoUML is a modelling tool that helps you design using UML diagrams
CLISP — a Common Lisp interpreter and bytecode-compiler
DJGPP — a 32-bit DOS port of GCC and other GNU utilities
Eiffel
Erlang
Experix — command line and stack system for data acquisition and analysis and graphics
Forth
GCC — a set of compilers for multiple programming languages and platforms, including
C
C++
Ada
Java
Pascal
Fortran
GT.M is an open source MUMPS (a.k.a. M) compiler for Linux
Harbour — compiler for the xBase superset language often referred to as Clipper
Jikes — Java compiler
LLVM — Optimizing compiler toolkit
Logo — Derivative of Lisp without parenthesis, for kids, with Turtle Graphics
MinGW — Windows port of +GCC
Mono development platform — Multi-platform .NET implementation (C#) based on the ECMA/ISO standards
MMIXware — simulator for MMIXAL language and MMIX processor
Objective CAML — a practical and fast functional OO language
Parser — a language for dynamic website creation
Perl — a programming language strong on text processing
PHP — a scripting language designed for web site applications
Prolog — Logic programming
Python — A high-level scripting language
Refal
Rexx
Ruby
StarUML — a software modeling tool and also platform that is a compelling replacement of commercial UML tools such as Rational Rose
Tcl/Tk — A high-level scripting language with a graphical toolkit

Bug Trackers
Bugzilla
Mantis
Trac
SharpForge

Code generators
Bison
CodeSynthesis XSD — XML Data Binding compiler for C++
CodeWorker
Flex lexical analyser
Kodos
phpCodeGenie
Ragel State Machine Compiler
Redet


Configuration Software
Autoconf
Automake

Integrated development environments
Main article: :Category:Free integrated development environments

Publishing
Passepartout
Scribus

Screen savers
Electric Sheep
Flurry
XScreenSaver
Boinc

Security

Anti-virus
ClamAV

Encryption
GnuPG
KGPG
AxCrypt
NeoCrypt
Seahorse
Windows Privacy Tray

Disk encryption
CrossCrypt
FreeOTFE
TrueCrypt

Firewall
Coyote Linux
eBox Platform
fdgw
Firestarter
FWBuilder
IPFilter
ipfw
IPCop
M0n0wall
PeerGuardian
PF
pfSense
Rope
SmoothWall

SSH
Lsh - server and client (supporting SRP and Kerberos autentication)
OpenSSH — client/server
PuTTY — client only
Cyberduck — Mac OS X client only

Other
Astro123 — Grep with a GUI
AstroGrep — Generate and read your natal horoscope.
BibleTime — Study Bible software
Bochs — PC emulator
Cygwin — open source Unix environment for Win32
Ebase — Open source constituent relationship management developed especially for non-profit organizations
Emdros — text database front end and back end
GNUpod — iPod database manager
gtkpod — iPod software
iPod Shuffle Database Builder
Kidzbrowser — Browser for children
Link Checker — checks HTML documents for broken links
MarZerUI — Application/File/Folder/Website manager for Windows XP computers
Memtest86 — stress-tests RAM on x86 machines
mywebcreator — A package for creating online diaries
Open Scene Graph
Project.net — Commercial Open Source Project Management
QEMU — CPU emulator featuring support for multiple architectures
refbase
SugarCRM — Commercial Open Source Customer Relationship Management
SuperKaramba Desktop widget integration in KDE
Treepie.sf.net — Folder size visualization
Vitrite — allows transparency in Windows 2000/XP programs
WINE — Windows executable support on Linux/BSD
WinMerge — highlights differences between textual files
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