I enjoyed this post by Candace Cameron Bure's Roo Magazine titled: "How to get a Personal Trainer in the comfort of your home." She has some great tips on how to get a great workout without the price tag of a personal trainer.
A great website she mentions is www.collagevideo.com, where you can see clips of different workout videos before you decide if it is something you will use and enjoy. Also, try the library too. They don't always have the video you want so the website above is another option!