If you’re using Google Reader for your RSS needs (and chances are you should), and if you’re like me on shortcut keys (love them, but can only learn them very slowly) you may be interested in the shortcut of shortcuts – ?
No, I’m not being quizzical. Just type a question mark while in the app and you’ll get an overlay of shortcut keys. Sadly it doesn’t work in Gmail, but when you’re trying to remember the shortcut for opening an item (v) it’s very handy.