Like 2manybikes, I've gone to kevlar. The front is a Schwalbe Marathon Double Defense; I don't recall what's on the rear. I've had no flats since, but I also haven't ridden through a noticable amount of glass or whatever, so who knows if they're working or my luck has changed. Anyway, I feel the tires were a good investment. In one period, I had 5 flats in 5 days. You don't get much riding that way.
Some people are like a Slinky ... not really good for anything, but you still can't help but smile when you shove them down the stairs.