Tracy Anderson is a celebrity trainer who trained Madonna for a long time, and is responsible for the sleek, tiny physiques of Gwyneth Paltrow, Courtney Cox, and a slew of other celebrities. I became interested in her method when she covered Fitness Rx for Women a while back and read about how she believed that any woman could change her body structure into the "teeny tiny" figure that Hollywood loves.
She's all about doing dance-inspired moves and lots of repetitions with low weights so as to exhaust the main muscles and engage the accessory muscles to create tone without bulking up. I've begun doing some of her exercises I found in various magazines and on youtube, and they've been so effective that I ordered her mat workout dvd on amazon and can't wait to get it. I'll post an update once it arrives and I have a chance to try it out.
You can learn more about her at her website.