I know some people are unhappy with the mouse speed settings provided by Apple's Mouse preference pane. There has already been a hint on modifying the preference file directly to achieve more speed. I recently purchased a driverless third-party mouse and was displeased with how painfully slow the mouse pointer moves in response to slight mouse movements, even with high speed settings. It made moving the pointer short distances to things like buttons and web links slow and tedious (see the posts by azerak and osos10 in the above hint.)
So I had an idea: what would happen if the acceleration value was negative? And, to my surprise, it did in fact reverse the acceleration behavior. Small mouse movements were much more responsive, while larger movements were slowed. For me this is a huge improvement, so if you're having the same problem this may be a solution. Right now I'm using a value of -0.3, but I'm still experimenting. It makes small moves quick and I can still move the mouse across my entire screen with relatively little effort.
A speed setting of 0.0 moves the mouse very slowly and ignores how fast the mouse is moving. Probably useless for most of us, but if you need precise movements (like maybe for drawing) it might be of interest.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030716013656515