If you would have asked this question two weeks ago I would have answered road only. But I picked up a free Raleigh Tangent MTB last week and after looking it over carefully I think I will rebuild it into a hybrid, street and off-road. It has cantilever brakes, Shimano Deore LX 21-spd, and Rapid Fire shifters which I think I am gonna like A LOT!
Although I plan to keep at least one road bike, at my age I think bending over into a racing position isn't as comfortable as riding upright again.
Steve