there's tonnes and tonnes of riding in Cham (and thats just the stuff i managed to find by bimbling around).
Lived there for 2 summers though sadly now rejoined the 'real world.' There is plenty of riding in Le Tour, Argentiere, Flegere, Les Houches etc etc. (there is also some pretty mental stuff at Brevent and some really fun bits in the bois du bouchet on the valley floor)
It is quite, err, how can i put it. umm 'relentless' – nearly every bit rooty or rocky or offcamber or for my lessthangodlike skills just plain difficult! I love riding in Cham and will be over for a few days in July but it is quite hard to get some flow on compared to say riding the PdS, Pila or Crans etc. You will have a ball though and there are a couple of facebook groups to tap into local knowledge. Or you could just prop up the MBC or the Monkey bar one evening for hookups the next day!
the new stuff at the back of Le tour is really fun and i think there might be a new trail up at flegere, dont know for sure though.
moon