Just want to throw in a good word for the 8 Min Fitness series: I love it. It's long enough that it does SOMETHING (not a lot, but something), and it's short enough that I can make myself get up one snooze cycle early to do it. Other DVDs have 15-20 segments, and 2 snooze cycles is just really pushing it!
Mandalinn pretty much covered it by saying you can't spot reduce and that only cardio will get rid of fat, but just remember that once the fat goes away you want the muscle underneath to be tight and toned. That's what 8 Min Abs can do.