This isn't only good for FCP's pull down menus but for Mac OS X in general. I can't believe I just learned about this the other month.
When you have a really long pull down menu, say the font list in Text generator, click on it to open the pull down then just tap the first letter of the name of the font you want. It will highlight the first font that begins with that letter (or menu item, this doesn't just work in the font menu).
Better yet, Up and Down arrow keys work as do the Home and End keys. No more mousing up and down hunting for the font or menu item you want.