When I was wasting the afternoon in Las Vegas the other day, I ended up going to an exhibit at the Guggenheim Las Vegas (inside the Venetian hotel) about motorcycles. It was pretty neat. Turns out the have a cool version of it online, as well (unfortunately, not directly linkable, but you'll find it). If you want to learn something about the history of the motorcycle and see some interesting machines, that's the place to go.