You've got a couple of choices. I have the Panaracer Ribmo's on my bike. Not the quickest tires but very flat resistant. I've heard the Schwalbe Marathon line are really good. I myself am looking into the Panaracer T-serv's or Schwalbe Big Apples. I think the Specialized Armadillo's are supposed to be very flat resistant, but not the greatest ride quality.