The Balme site

Green DH - The Marmottes is a green graded downhilll 2.5 km ride with 363 metres of vertical descent.
Blue DH - The Chevreuil is a 2.5km blue graded downhill track with 348 metres of vertical drop.

The Houches site

Chamonix Valley Rides - This is the valley floor area. Popular MTB trails are the Petit Balcon Sud or Petit Balcon Nord.
Le Brevent & La Flegere Mountain Bike Trails - Accessed via the Brevent or Flegere cable car. Steep and challenging with tight switchbacks.
Les Grand Montets Mountain Bike Trails - Accessed from the Lognan cable car. Technical descent with tight switchbacks.
Le Tour Mountain Bike Trails - Easier MTB riding. Greens accessed from the Charamillon gondola and the Autannes chair lift. There is also a blue trail here.
Vallorcine Mountain Bike Trails.
Servoz Mountain Bike Trails.

If you have ridden any of the MTB trails in Chamonix then please share you experiences and add some pictures, videos or a review to the listing.