There are some NP's I still like to visit but you're right, they aren't dog friendly. If one is in my path and there's not too many people, I'll stop for a few days of R&R. It sucks but Yellowstone nowadays I avoid like a big city. It's great in the winter though if you can get around but the rest of the year it's jam packed with foreign tourists who think it's a big petting zoo. I've also managed to find great spots just outside many of the parks in a NF, or I'll try to hit one of the more primitive/outlying not as popular camp sites.
I used to love going to Yellowstone and was employed there for a while in 1995. Every time I go back now it's a giant tourist trap of foreign nationals that soak up all the camping and turn the place into a giant madhouse parking lot and then of course, there are those folks who treat it like a giant petting zoo.
Oh, don't get me wrong, Yellowstone is an amazing and spectacular place to visit with many incredible geological features, but I'd suggest going in the off season. In actuality the wintertime is one of the most incredible times to see it. If you plan on camping there definitely make reservations way in advance.
