Address Book data is kept in your user folder but keeping a vcard backup copy is never a bad idea since it takes up no space at all.
Mail, iTunes, Safari prefs, keychains are all in your user folder. You'll have to check for the rest of your apps in /Users/youruser/library/preferences/ if you aren't sure. I'm not sure about SteerMouse. If its a prefpane its prefs might be in the root library folder.
The vast majority of what you want is in your user folder.