A short list of web sites for annual rendezvous events. Some sites will have lists of other rendezvous:

Rendezvous Events
Rendezvous Country
Mountain Man Mafia
Red Hawk Trading Rendezvous events
Red Lodge Rendezvous, in Red Lodge, Montana.
Corps of Discovery Rendezvous
1838 Rendezvous, Riverton, Wyoming.
Fort Bridger Rendezvous, Wyoming.
The Green River Pageant, an outdoor pageant of the fur trade era,
each July in Pinedale, Wyoming.
The Frozen Toes Rendezvous, usually held in February in Colorado.
The Rocky Mountain National Rendezvous in July,
usually in Wyoming, Colorado or Utah.
The High Plains Regional Rendezvous in June, held in Nebraska,
North Dakota, South Dakota, Kansas or Minnesota.
The Pacific Primitive Rendezvous in June in Idaho.
Old Northwest Territory Primitive Rendezvous
Southeastern Primitive Rendezvous
The Fort DeChartres Rendezvous, at Fort de Chartres, a partially reconstructed 1760's stone fort built by the French colonial government. Prairie du Rocher, Illinois.
Prairie Villa Rendezvous, on St. Feriole Island, Prairie du Chien, Wisconsin.

The Smoke and Fire News newspaper also lists mountain man rendezvous and other fur trade era events.