Here is a list of essential freeware (or at least free somehow) apps for Mac OS X I install on every new machine. I figured theres plenty of these lists for Windows stuff, but not many for Mac, so I made one for all you OS X users out there.

System
ButlerThis is the most awesome app ever conceived.  Will replace LaunchBar or Quicksilver and add the functionality of several other apps, using up practically no memory! Universal binary too.http://www.petermaurer.de/
MenuMetersIf you like to keep an eye on whats going on under the hood, this is pretty useful. Universal.http://www.ragingmenace.com/
SysStat NanoThis is a Dashboard widget which can show every stat about your computer at the click of a button. Universal binary.http://www.islayer.com/
ClamAVIf you are worried about viruses, here is a free scanner.http://www.markallan.co.uk/
HenWenIntrusion detection system for the paranoid.http://seiryu.home.comcast.net/
OSXvncIncredibly useful if you want to access your computer from away from home. UB.http://www.redstonesoftware.com/
Chicken of the VNCUse this when away from home to view your VNC session. UBhttp://sourceforge.net/
Carbon Copy ClonerEssential tool if you want to clone your drive. Also try NetRestore.http://www.bombich.com/
FinkGreat tool to make it easy to install the wealth of open-source command-line utilities etc.http://fink.sourceforge.net/

Browsers
FirefoxOne of the best browsers on the planet, with hundreds of plugins. Universal binary herehttp://www.mozilla.com/firefox/
CaminoFast, slick browser, and very functional too.http://www.caminobrowser.org/
OperaThis browser works on anything. They're even building a browser for the DS.http://www.opera.com

Internet/Network
CyberduckExcellent easy to use FTP and SFTP client. Universal binary.http://cyberduck.ch/
FuguAnother great FTP/SFTP application.http://rsug.itd.umich.edu/
TransmissionVery simple and fast BitTorrent client. Universal.http://transmission.m0k.org/
PureFTPd ManagerThe most perfect FTP server software out there and a sweet GUI on top of it. If you wanna FTP, get this.http://jeanmatthieu.free.fr/
AdiumAwesome multi-protocol Instant Messaging client. UB as well.http://www.adiumx.com/
SkypeMake internet calls for free, or calls to anywhere in the world for dirt cheap.http://www.skype.com/
ColloquyNice looking, simple, full featured GUI IRC client. UB.http://colloquy.info/
ViennaVery nice RSS newsreader. Can you believe all this cool stuff is free?http://www.opencommunity.co.uk/
gDiskAmazing little tool lets you use your gmail account as storage space.http://gdisk.sourceforge.net/

Video
VLCThe swiss army knife of video players. Can play almost everything except new WMVs. Required. Universal binary herehttp://www.videolan.org/vlc/
HandBrakeThis is the VLC of DVD video encoding. It will take a DVD  and convert it into almost anything else. Universal.http://handbrake.m0k.org/
iSquintThis will convert almost any video to a video iPod compatible format. Universal as wellhttp://www.isquint.org
Handbrake LiteConverts DVD directly to iPod video format. UB.http://www.isquint.org/
MactheRipperVery useful if you just want to copy your DVD's to your HD to view later.http://www.versiontracker.com/

Audio
AudacityCross-platform audio editing tool. Very useful for chopping audio or changing formats etc. Capable of multitracking too.http://audacity.sourceforge.net/
MidiKeysLets you use your computer keyboard to send MIDI signals.http://www.manyetas.com/
Crystal VSTWicked little freeware synth program. Very powerful. Rax will let you try this out. UB. http://www.greenoak.com/
AcquisitionFast LimeWire and other P2P network client. UB.http://www.acquisitionx.com/
xFactorThe same as above, but does some other cool stuff. UB.http://www.xfactor.cc/
WireTapLets you record audio from any source or application. Very useful for recording internet streams.http://www.ambrosiasw.com/

Editors
TextWranglerIf you need something more than TextEdit, this is a wicked editor with more advanced functions.  Kicks ass. Universalhttp://www.barebones.com/
SubthaEditAnother excellent alternative to TextEdit. Universal too.http://codingmonkeys.de/
NeoOfficeJava implementation of OpenOffice.org for OS X. Nice.http://www.neooffice.org/
NvuFull featured, fast cross-platform HTML editor. Why pay for Dreamweaver when this is free?http://www.nvu.com/
GIMPshopAlmost all of the features of Photoshop at an infinitely smaller price. Requires X11 but thats on your OS X install disc.http://plasticbugs.com/
Blender3DIf you have time to do 3D, this is an excellent tool to make 3D stuff with for free.http://www.blender.org/
Google EarthThis isn't really an Editor, but its extremely cool nonetheless.http://earth.google.com
iPhoto BuddyIf you have a LOT of photos, this will let you manage multiple photo libraries.http://nofences.net/

You may think this site is ugly, but I wanted a low bandwidth, simple list, and thats what this is.