The old Firm Classics are excellent DVDs--here's an example of an excerpt of one of my favorites. The settings and outfits are hokey--but the workouts are pretty effective. The newer Firm videos, not so much. They usually require a step and dumbells. These old videos are designed to be both aerobic and weight training.
The Tortoise w/ Tracy Long is much more beginner friendly. The actual workout is 1 hr total, including stretching and warmup.
I'm going to check out Jillian Micheals--I've never seen one of her videos.