Free and open-source software is good for you and good for the world. This is the best free Mac software that we know of.
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.Download Page
IM - Instant Messaging
Adium
Connect to multiple IM accounts simultaneously in a single app, including: AOL IM, MSN, and Jabber. Beautiful, themable interface.Download Page
Application Launching
Quicksilver
Quicksilver lets you start applications (and do just about everything) with a few quick taps of your fingers. Warning: start using Quicksilver and you won't be able to imagine using a Mac without it.Download Page
Mozilla Thunderbird
Powerful spam filtering, solid interface, and all the features you need.Download Page
Utilities
The Unarchiver
Uncompress RAR, 7zip, tar, and bz2 files on your Mac. Many new Mac users will be puzzled the first time they download a RAR file. Do them a favor and download UnRarX for them!Download Page
DVD Ripping
RSS
Peer-to-Peer Filesharing
Running Windows Software on Macs
Q Emulator
Run Windows programs on your Intel Mac at near native speed. Works on G4 / G5 Macs too, but much slower.Download Page
Podcasting
Video Player, Torrents, Podcasting
Miro
Beautiful interface. Plays any video type (much more than quicktime). Subscribe to video RSS, download, and watch all in one. Torrent support. Search and download from YouTube and others.Download Page
Telephone
Telephone
A great "SIP" client. Call regular phones from your Mac. 100% free and open source.Download Page
Financial Transactions
Bitcoin
A "peer-to-peer" digital currency so you can buy things without paying transaction fees.Download Page
Video Converter, iPhone Converter
Miro Video Converter
Convert any type of video to mp4 or theora. Convert any video for use with iPhone, iPod, Android, etc. Very clean, easy to use interface.Download Page | Mac App Store (free)
Video Playback
VLC
Plays more video files than most players: Quicktime, AVI, DIVX, OGG, and more. Pretty good interface.Download Page
MPlayer
The interface and buttons are not as nice or as Mac-like in feel, but it may play even more video files than VLC.Download Page
Perian
A plugin that allows quicktime to play additional video formats. (Included in Democracy Player.)Download Page
iPod Ripping
CD / DVD Burning
Privacy
Vidalia
This TOR frontend keeps you anonymous on the web using military-grade techniques. For use with Firefox see: TorButton.Download Page
Word Processing / Office Suites
LibreOffice
Big, full featured suite of tools for word processing and spreadsheets. Compatible with and a free replacement for Microsoft Word, Powerpoint, and Excel. Friends don't let friends pay for Microsoft Office.Download Page
AbiWord
A word processor. Leaner and quicker than OpenOffice. Compatible with Microsoft Word documents and OpenDocument Format.Download Page
Wifi Scanning
Sound Recording
Graphics, Photo, Publishing
FTP / SFTP
Fugu
Not as polished as Cyberduck (and only for SFTP) but has a side by side interface showing your files and the remote files.Download Page
HTML / Text Editing
Blue Griffon
Visual tool for making websites (WYSIWYG html editor), comparable to Dreamweaver.Download Page
IRC
Web Development
WaveMaker
A visual development tool for building great-looking web and cloud applications.Download Page