Tip level : pro
Required : Terminal, Panther
Related link : Switch Terminal window focus with mouse movement
You want to be able to input commands in the Terminal without even making it the frontmost application ? You can if you turn on this hidden feature with the following command :
defaults write com.apple.Terminal FocusFollowsMouse -string YES
Relaunch Terminal before to activate it. If you have more than one Terminal window opened, you’ll be able to enter text in one by moving the cursor above it (notice the window activates when you do this : shadow and title bar appearance are modified). This can even be used when you are in an other application, but it seems to be somehow unpredictable when more than one window is opened (I think you need to wait a few milliseconds for it to work well !).