Stop the Lion "rubber-band" bounce
One thing that annoys many Lion users is "rubber-band scrolling": When you scroll to the end of a page in many apps, the page seems to continue scrolling a bit, then bounces back. OS X Hints reader Havner found a way to remove this effect. (He started from this anonymous hint about turning it off in Xcode, then did some research on Apple's discussion forums to find the answer for other apps as well.)
As with so many other 'hidden' settings in OS X, the fix for this is just a Terminal command away:
defaults write -g NSScrollViewRubberbanding -int 0
In Terminal, enter that command then press Return. It should stop the behavior in the Finder, Mail, Preview, and TextEdit, among other applications; it does not, however, work universally, Safari being one notable exception.
If you want to revert to the standard bouncy behavior, just run this command in Terminal:
defaults delete -g NSScrollViewRubberbanding
In both cases, you'll need to quit and relaunch any applications that displayed the rubber-band effect. If you find that this works with more than the applications listed above, post your success stories in the comments below.