My current favorite to use is the Video Essentials II. Lots of incredible explanations of how a system comes together, and very cool graphics. Among other things, the audio-testing portion of the disc will also allow you to do frequency sweeps on each speaker. With an SPL meter, this allows you to note peaks and valleys in your system's frequency response so you can make any necessary adjustments, like moving the sub or speakers to a different location, or adjusting the crossover on the receiver or sub.
AND, it has a couple very cool demo tracks. Track #2 is unbelievably cool. It's about 20 seconds, but it will seriously rip the plaster off your ceiling. 
Cheers!!