Here's a couple settings I find particularly helpful when working in the Terminal on OS X. The first turns on case-insesitive tab completion (for bash at least, I haven't tried it in other shells.) The second turns on Focus Follow Mouse for the Terminal only. While the Terminal's in the foreground, it will have focus regardless of mouse position, but with this setting, you can send key events to a Terminal window that isn't in the foreground by hovering the mouse cursor over the Terminal window.
echo "set completion-ignore-case On" >> ~/.inputrc
(via Case insensitive completion in 10.3)
defaults write com.apple.Terminal FocusFollowsMouse -string YES
(via Switch Terminal window focus with mouse movement)
Both of these are still working for me in 10.4.