Yellowstone was really fantastic. Because our lodging was so far away, we couldn't really get into the park before the sunrise, but we did three sunsets there and had unique photographs each evening.
On our first trip, we drove by Lewis Falls - there was a quick little trail that takes you to this viewpoint, which is much better than from the road.
Across the river from the Grand Prismatic Spring, there's this interesting bit of runoff that goes into the river. The sun was peeking through the clouds when I took this picture.
On to West Thumb Geyser Basin - there are a lot of little pools here. Fantastic place to walk around.
On a different day, we visited Old Faithful a second time (much more interesting than the first).
After the sun went behind the hills at Gibbon Falls, there were a lot of nice details to see.
The following two photographs are from the Firehole River Drive.
On our last evening in Yellowstone, we went down Firehole Lake Drive just to see what was out there. When we saw the Great Fountain Geyser, we knew we had a place to shoot sunset. There were a handful of photographers there when we returned later in the evening (turns out we weren't the only ones to think of this). We got a little bit of light, and then the geyser erupted (we still have spots on our car!).