In reply to Doghouse:
Up to Brevent, down from the Col du Brevent towards the Refuge du Mode d'Anterne, up towards Le Catedral and the other limestone spires north-west of Mont Buet (I forget the name of the refuge to the west of Le Catedral and don't have my map handy), up Buet via the spicy north ridge and then down towards the refuge in the Berard valley, OR miss out on Buet and head east to Cheval Blanc and the dinosaur footprints, then down to the Chalets de Loriaz via either the Col de la Terrasse or the Gorges de Veudale, then back to Chamonix via either the Col des Montets or up over the Tete de Balme.
There are various refuges and bivouacs along the way, you could drag the route out for over a week, or you could jog it in a long day.