Dance Central may well be one of the best dancing games out there but you'll still have to flail around in front of your Kinect sensor whilst playing it, which should be fairly amusing for anybody who's watching you. There are plenty of tracks to chose from, so this one should last you a fair while. Currys are currently parting with copies of the game for £9.97, which should make you a saving of almost £5 on the next best offer coming in from Simply Games. Thanks to ettienem1001 @ HUKD.
Harmonix' emergent dance phenomenon is probably still the closest thing Kinect has to a killer app, and is one of the best music games out there. Physical routines, intelligent body tracking and a wealth of content ensures that this is surprisingly good value for even the most jaded and overweight gamers (i.e. me), and an absolute blast at parties. Bee.com are charging £24.99, which undercuts the competition from Amazon and subsequently everyone else.
And yes, I am the worst dancer ever.