I was just down in Yellowstone a couple of weeks ago. Haven't posted any of the pic's yet but it was a cool trip. Hit the Yellowstone River just outside the lake on the day it opened, pretty busy but some nice sized fish in there for sure. Also some cool views, small geysers (sp), buffalo, etc. Lot’s of anglers as well though. Yellowstone is a busy place in general. But like every where, walk far enough and the "crowds" thin immensely. I also tried the Firestone River in Yellowstone but the water was so hot I quit. I don't know what the weather's been like lately but lots of rivers had voluntary closures from noon-6 or 8 PM. The Upper Madison is also there but because of the temps I didn't even wet a line... definitely strong evidence to support my case for a return trip. In Grand Teton there is the Grade Verde or something like that. I don't know how mobile you'll be while you're there but the Snake River tail out outside Jackson (just inside Idaho) is supposed to be unreal. Yellowstone regulations are unique, can't fish before 5 or 6 AM or after 10 PM. Send me a PM if you want more info, I think I still have a copy of the reg's and some maps some where around here.