Here's a nice one, hold your finger over the 9th frets on the top two strings. Then strum these two to create a harmonic, then dive, it sounds cool when the two notes go out of tune from each other on the way down... if you want to go backwards, it can be easier to dive the trem forward a bit before hitting the harmonic then diving backwards.. gives you more slack to play with and saves the chances of breaking a string or going out of tune (if you have a dodgy trem system).
Those dives sound best on the harmonics of the follows frets: 3,5,7,9,12,15,17 and 19
For something a little different, try a dive on the 3rd fret harmonic on the low E... it sounds great if you dive into an open E power chord (or over the chord)...