in addition to the danos (which i haven't tried, but hear good things about), and the tonerider (which i haven't tried, but i have the chorus, which is very good), the biyang overdrive od8 might also be worth a look. I got one recently, it's pretty nice. It sounds like a tubescreamer (to my ears, and without a tubescreamer on hand to compare it to head to head), but has a bit more versatility in that it has 3 different modes, and swappable chips, to let you fine tune the tone. I like mine, anyway. I'm not sure if they're bulletproof in the way that the really expensive boutique stuff is (my biyang fuzz's LED went dodgy, I've got a replacement on the way), but they sound good, anyway, to my ears and are reasonably inexpensive. That's assuming you like TS-style overdrives, of course. :)