I've bought recently a Macbook Pro and was very annoyed by the cursor acceleration of Mac OS X: Either the mouse cursor was moving very slowly or (if you moved the mouse faster) jumped nearly from one screen edge to another.
Luckily I could solve this problem now. You can download a file name "killmouseaccel.tar.gz" from this forum thread (somewhere in the middle). It contains the program killmouseaccel. You have to start it from a terminal:
Instead of "mouse" you can also specify "trackpad" or even both. For me this program works very well and it is free unlike most other solutions (e.g. USBOverdrive or SteerMouse).