Web Browsing
Mozilla Firefox
The premier free, open-source browser. Tabs, pop-up blocking, themes, and extensions. Considered by many to be the world’s best browser.
Video Player / Video Podcasting
Miro
Beautiful interface. Plays any video type (much more than windows media player). Subscribe to video RSS, download, and watch all in one. Torrent support. Search and download from YouTube and others.
IM – Instant Messaging
Pidgin
Connect to multiple IM accounts simultaneously in a single app, including: AOL IM, MSN, and Jabber.
Mozilla Thunderbird
Powerful spam filtering, solid interface, and all the features you need.
RSS
FeedReader
Simple, lightweight aggregator.
RSSOwl
Solid cross-platform RSS client.
Peer-to-Peer Filesharing
Cabos
A simple, easy to use filesharing program. Gnutella network.
Gnucleus
A very good Gnutella search and download filesharing program.
Azureus
A powerful, but complicated BitTorrent client. So many features you’ll lose your mind.
Video Playback
VLC
Plays more video files than most players: Quicktime, AVI, DIVX, OGG, and more. Pretty good interface.
MPlayer
Similar to VLC– plays loads of video formats.
Media Player Classic
Compact, but powerful media player. Plays anything under the sun. No install necessary.
DVD Ripping / Video Conversion
Media Coder
Great tool for ripping CDs, DVDs, etc and converting between tons of video formats.
Word Processing / Office Suites
OpenOffice.org
Big, full featured suite of tools for word processing and spreadsheets. Compatible with and a free replacement for Microsoft Word documents. Also supports OpenDocument Format.
AbiWord
A word processor. Leaner and quicker than OpenOffice. Compatible with Microsoft Word documents and OpenDocument Format.
Podcasting
Juice
Solid podcasting client.
DVD Ripping
Handbrake
DVD to MPEG-4 ripper/converter.
Sound Recording
Audacity
Simple sound recording tool.
Graphics / Photo Editing
GIMPShop
Photo editing application that rivals Photoshop in features.
Paint.net
Graphics editor with a very nice interface.
Inkscape
Vector graphics application.
FTP / SFTP
Filezilla
Excellent FTP program.
IRC
X-Chat 2
IRC client.
More softwares from Open source windows