A "sport" touring frame is a pretty classic design for long-distance events. It typically comes with long reach brakes and eyelets so that you run a little fatter tire (700 x 28c) and fenders. Plus you can mount a rack. Trek made a number of sports touring bikes that have become classics.

If you like your rivendell, why not a soma san marco or a soma stanyan? I really, really don't need another bike but I've thought about the soma san marco esp. since it now comes in what I think is a prettier color. You'll pay a premium for the frame but it is nicely thought out.