You can't go wrong with Jillian Michaels. Her DVDs are less than $10 at Wal Mart and crazy good, as long as you're not looking for Insanity of P90X. I love her 30 Day Shred, Ripped in 30, and Yoga Meltdown. Her Burn Fat, Boost Metabolism is 50 (ish) minutes of hardcore cardio, but I haven't tried that yet. I don't think she has a bad DVD out, to be honest.