McBoo, did last year – absolutely brilliant (if you like that sort of thing)
Just register yourself through sport communication – the tour packages can work out very expensive
Get a hold of the on-line alpe d'huez tourist information and they can sort you out with accommodation or try King of the Mountains who run a Marmotte special (I stayed there the Fiday – Sunday and would highly recommend them – run by an english couple – Guy & Helyn – food is excellent – they also do airport transfers depending on where you fly to)
BUT would recommend you make your entry as early as possible to get an earlier start number – with 7000 cyclists on the road, the descents can get a bit hairy & the feed stations get very hectic the further back you are.
The atmosphere throughout was great, the views from top of the Galibier were stunning, and the crowds the whole way up the Alpe were brilliant – a very memorable day