software for OS X

$ = requires key for unimpeded operation

sources

MacUpdate | VersionTracker: reviews and links to popular software updates
HyperJeff: database of OS X software (comprehensive and unusual)
GNU OS X Archive: GNU unix software ported to OS X and packaged for use with the Apple Installer
MacPorts | Fink: package management systems for open-source unix software ported to OS X

LaunchBar: $ : very useful, quick, configurable keyboard access to find/open/manipulate files/programs (free alternatives: Butler, Quicksilver)
Butler: provides many useful features but I use it simply for it’s excellent multiple clipboard/pasteboard support
OnMyCommandCM: make your own system-wide contextual menu commands
Pixture Studio: excellent contextual menu plugins (PhotoToolCM, QuickImageCM, QuickPlayCM, CalculateSizeCM)
TextExpander: $ : use abbreviated triggers to insert predefined text snippets, and more (preferred over TypeIt4Me)
DEVON technologies: useful service modules (CalcService, WordService)
MenuMeters: CPU/memory/disk/network info in menubar
MenuCalendarClock: $ : replaces menubar clock; includes a drop-down calendar with links to iCal (it remains useful without key)
DiskWarrior: $ : repairs HFS+ volumes (where others fail or make matters worse)
ClamXav: virus scanner (GUI for the ClamAV open source antivirus engine)

SideTrack: $ : configure trackpad for scrolling and button areas
DoubleCommand: remap keyboard (e.g. remap that useless “enter” key to “option”)
Screen Spanning Doctor: firmware patch allows many iBook/iMac/eMac models to drive external displays separately (like PowerBooks do, without mirroring)
Anacron: automatically runs regular maintenance procedures which are not run if the computer is turned off (or sleeping) at night; this is not needed for 10.5 (Leopard) or newer

Little Snitch: $ : internal firewall (for detection/prevention of network connections from the inside out)
VNC client & server: excellent protocol for remote GUI display/control (developed by AT&T); use TightVNC for MSWin and unix
CyberDuck: FTP and SFTP client
NetNewsWire: $ : RSS/RDF client (free “Lite” version also available)
PithHelmet: if you use Safari; a potent content filter to remove advertising and more…
Saft: $ : adds many useful/missing features to Safari, especially: state persistence (windows/tabs which are open when Safari quits/crashes will be renewed at next launch); Safari is not useful to me without these essential features
browser plugins: fast and clean solution for PDF and MS Word files
Adium X: instant-messaging client supporting most protocols (AIM, ICQ, MSN, &c.)
Meteorologist: current weather information and forecasts in dock or menu bar (supports cities around the world)
RadioRecorder: saves network audio streams to MP3 files (CLI version: StreamRipper; also available from MacPorts)

HexEdit: hexadecimal file editor
skEdit: $ : a promising text editor with (X)HTML & CSS tools, excellent extensibility, and SFTP integration
AppKiDo: efficient browser/interface for the Cocoa reference documentation (installed with Developer Tools)

VLC | MPlayer OS X: multimedia players for various audio and video formats including most Windows Media files
Flip4Mac WMV: QuickTime component to play Windows Media video and audio files
Perian: QuickTime component that adds native support for many popular video formats
Cog | Play: audio players that support many file formats (which iTunes & QuickTime neglect)
Max: for creating high-quality audio files in various formats (such as FLAC), from compact discs or files

cocoAspell: augment Apple’s spelling service (use dictionaries for many unsupported languages, including improved English dictionaries)
DICTatoro: complete offline dictionary (DICT) solution (installer package includes server, dictionaries, reader); note: Tiger includes a dictionary, though the source is different
SmallScreenX: for previewing windows at smaller screen sizes
MConvert: $ : unit conversion utility (alternative: try the units command in the Terminal)
VoodooPad: $ : powerful personal notepad with wiki-like page creation/linking, object embedding, integrated sketch, and more