I've been reading a lot of blogs by people who ride long distances on their bikes (Matt Chester and Kent Peterson). The Great Divide Race last year sounded superb (Canada to Mexico along the line of the Rocky Mountains), and races like Trans-Iowa and Ride Across INdiana. There was a longish Scandinavian race for fixies too, Le Tour Retard(?). And I've read a bit recently about the early days of the Tour de France that makes the current race sound really tame.
A colleague of my dad's rides brevets, audax (audaxes?), randonees (basically long rides with checkpoints), like London-Edinburgh-London. Mad distances.
After riding some Sustrans routes, I've had a few ideas for long MTB 'races' (though I use the term loosly), across the North East. I was thinking of things like Barnard Castle-Bishop Auckland-Sunderland along the W2W Sustrans route with checkpoints along the way (or tasks, like noting down collection times from specific post boxes).
I just found a page with a set of ideas, all of which sound pretty cool, randoneé + alleycat. Great quote:
It's like a horrible auto wreck between a car driven by a French randonnée and one driven by an alleycat race. One part long-distance, self-supported fast touring, one part on-the-fly, all-out speed driven routing. A match made in heaven? A recipe for disaster?
Anyway, just rambling thoughts.