You probably already know this, but I just wanted to point out ... you can't trim down a specific body part by exercising. What excercise can do is make the area stronger, build up the muscle (thus making it look firmer), and burn calories which may help you lose additional fat all over.
Any good general weight training video will include good lower body exercises. I like Kathy Smith's videos overall the best ... you might take a look at her Lift Weights to Lose Weight 2, also the original Lift Weights to Lose Weight. The second one is more innovative as it incorporates Pilates principles, which are GREAT for lower body. She has an older video called Secrets of a Great Body - Lower Body that I like a lot. You might also check out her Pilates for Lower Body. You can see descriptions, reviews, and see film clips of all her videos at
http://www.collagevideo.com/cart/default.aspx. Just put a check by her name and click on the Show me the Videos button.