A common problem that I have with SSH is what happens when I disconnect from a network without with a SSH session still open - the SSH session won't exit and Ctrl-C/Ctrl-D/Ctrl-Z/Ctrl-\ won't kill it.
I always used to just close the terminal emulator when this happened, but I recently figured out how to exit a dropped SSH session!
The way to do it is to press <Enter> (to make sure you're on a new line) and then ~.. The ~ is a special character that tells SSH that a command is coming that should be handled by ssh itself, and not sent over to the remote computer. There are actually a ton of these commands (You can press ~? for a full list), but the main one that looks useful to me (aside from ~.) is ~<Ctrl-Z>, which sends a SSH session to the background (Just like pressing Ctrl-Z would for a local process.)
As I use Linux more and more I keep finding more neat, but kind of hidden things like this - maybe I should do a post on cool linux/POSIX terminal stuff someday :)