l’Alpe d’Huez, les Deux-Alpes, Montgenèvre, Puy-Saint-Vincent and Serre-Chevalier are launching a common mountain bike lift pass for next season (June 2010). The pass is known as the Grande Galaxie - Planète VTT and will give access to 400 km of trails and 27 lifts for a total of 35km of vert.
There will be two version, a 6 days pass and a summer pass (mid June to mid September - unfortunately not including the winter :-( ). You can buy it in any of the Galaxie resorts but the price will vary depending on the home resort, for example 45€ for 6 days and 90€ for the year if you buy in Puy-Saint-Vincent which is the best value.
Now if only some of the small ski areas could get together to offer something similar.