I like to use pops and locks, so I'll probably buy some of Sadie/Kaya's DVDs. I'm lucky enough that they're currently my teachers, and they KILL us with the warm ups and drills! I'm sore 3 days after class. Every week.
If pop & lock is a technique you like, you may want to consider Elisheva's Tribal Fusion Bellydance - Pop & Lock dvd. She knows her stuff, explains it in a clear manner, and then drills, drills, drills.