Most of the classic alpine cols follow very easy to navigate country (seeing as how there is normally only one or two roads over the big passes), so I normally just use a standard road atlas to locate the passes and then use
http://www.climbbybike.com to sort out the rest - which is the best direction to go, average gradients, climb profiles, etc, etc. Also the book Tour Climbs by Chris Sidwells is very useful to help plan rides and sort the really good cols from the also rans (although you will still need a road atlas to help with planning the routes, and good luck to you if you feel the need to take the book with you....its massive!) You won't need any sneaky info on back roads like you do in the Peak. A lot of the tourist info offices have maps for cyclists - the one in Bourg d'Oisans was very helpful when I was there last year.
I can highly recommend a few days getting your eye in, before the classic loop starting from Bourg d'Oisans, up the Croix de Fer, pootle down t'other side, then up the Col de Galibier, down the Col de Lautaret and finish up Alp d'Huez.
A week in the alps - I'm well jealous. :'(
