Funny you should ask...I actually got a bike yesterday, but being that I was ~350 when I originally posted this and I'm now around 75 lbs less, I didn't get one that was specifically designed to be overly tough.

A friend of mine was selling his bike super-cheap - a Kona Dr. Dew, which is somewhere around $1,000 new and after the extras he put on it he'd probably spent around $1,250-$1,300 on it. He sold it (and extra tires, a helmet, a pump and some other random stuff) for $250, which was obviously a deal I couldn't turn down. I've yet to do more riding on it than around the parking lot at his apartment complex, but it seems really nice.

If I *had* gotten a bike back then, though, my research indicated the the Kona Hoss was the way to go - it's built to be very, very rugged. The main thing that I've learned is that you need to be very concious of keeping the tires fully inflated whenever you ride it.

Good luck-

-j.