For those who like the idea of a mountain bike trip but are leery of singletrack, look into the trips which are held on dirt roads like Telluride to Moab, Backcountry Hot Springs (in Idaho), the Yellowstone trip (I think), White Rim, etc. These are good trips for roadies who want to get off the asphalt but not onto their a$$es.

Both Western Spirit and Rim Tours are excellent companies and can steer you toward the right trip for your abilities. Don't think that a mtb tour always requires huge technical skills and the ability to leap large boulders in a single bound.