Nashbar has some nice inexpensive 26x1.25" slicks that work well for me. I think they're rated to 90 lbs. They've been pretty good in my urban environment until a couple weeks ago on a short jaunt, where I somehow managed to find the only goathead bush in the city. Got five holes somewhere along this one mile stretch, with four of the goatheads still in the tires. Over the last ten years in this city, I've never seen a goathead here, so it may have just been a fluke. A heavier tire may or may not have survived, as those thorns were pretty mean.