I hear the new Hannah Waterman one is good.
I have the original Ministry of sound pump it up which is good fun and gets you sweating and it's a laugh too, even if you jump or step on the spot whilst they do moves you can't figure out, lol.
I just bought the new Clubland one because the newest ministry of sound got bad reviews and the clubland one is Deanne Berry who did the original MOS one and does the stuff on GMTV. It was only £9 from hmv online but I've not had chance to try it yet.