Jillian Michaels "30-day Shred" is a great workout DVD - one of my favorites! I *love* that it's only a 20-minute workout and makes the most of your time...but don't be fooled! It's not an easy peasy 20 minutes -- it's a great intense workout (that you can work up to) and it gets results!
I compared lots of prices when I bought this last year, and I believe this is the cheapest I ever saw it -- $6.99 (and qualifies for Free shipping on orders over $35)!
*If you're looking for something to get you to the free shipping threshold, I have friends that also had great results with her other DVD's - 6 Week Six Pack, and Ripped in 30!