There’s now an awesome program to disable mouse acceleration in OS/X. It’s a very simple executable that you can load at login. No more, no less 
You can get it here: https://github.com/cdown/mac-cel
With the recent release of Portal and Team Fortress 2 for the Mac I’m guessing there are quite a few gamers that have noticed the horrible acceleration that’s default on OS/X.
I’ve finally managed to find a little tool that can give you 1:1 mouse/pointer movement, just like you can on Windows (with the help of some regtweaks and system file patchers).
Download this Preference Pane and run it: MouseAccelerationPref11c
Use these settings:
I know it says ‘Inverted’ on -6.0x, but it’s actually 1:1 non-inverted 😛