Here’s a little discussed feature of Time Machine in OS X Leopard. It works directly with some applications!
If you open Mail.app for example, and launch Time Machine from its menubar item you can directly access and recover individual email messages. The alternative would be using Time Machine to recover your entire ~/Library/Mail folder, which isn’t very practical. I’ve tested several other applications and so far I’ve found that this also works for Address Book to recover contacts and groups, and iPhoto to recover photos and albums.
One caveat I’ve found is that you need to use the menubar item to launch Time Machine, otherwise a Finder window opens and it doesn’t activate properly. Other than that, this seems to be an excellent use of Time Machine! Please feel free to leave a comment if you discover any more applications this works with.