Damaged Fonts -- Lloyd Lim <email@example.com> says that a good check for bad font files, along with other files with resource forks, is to run John Norstad's excellent virus fighter, Disinfectant (now at version 3.2, see below), which checks for and reports damaged resource forks. It may not catch all types of damage, but it is a useful troubleshooting tool.
Avoid Simple Typos
If, like me, you find yourself typing 2911 in place of 2011 entirely too often, you can have Mac OS X (either Lion or Snow Leopard) fix such typos for you automatically. Just open the Language & Text pane of System Preferences, click the Text button at the top, and then add a text substitution by clicking the + button underneath the list. It won't work everywhere (for that you'll want a utility like Smile's TextExpander), but it should work in applications like Pages and TextEdit, and in Save dialog boxes.