Several of the workout DVDs in my collection feature Ellen Barrett (some of them are from the Crunch series; others are from her own studio).
Ellen is a pleasant instructor -- quite enthusiastic, but generally not excessively so -- and the exercises she offers are challenging without being frustratingly difficult. She tends to feature slightly longer sets of things than you might find in your typical exercise DVD, which is good for folks like me who take a few tries to get the hang of things.
I like Burn & Firm Pilates because it includes some exercises with arm weights, integrated into the flow of the workout. The DVD gets your heart rate up moderately while also incorporating some flexibility and strength training.
Reviews here, here and here.