Outstanding!
I am going to try not to duplicate what cogitator had to offer. His advice was excellent so I am only going to comment on some other aspects. If you have any additional questions, ask away here or via freepmail.
Couple of key points: Bring some warm clothing. Temps ran from low 70s, high 60s during the day to high 30s, low 40s at night. It was light out until 9:45 and the sun started to come up around 4:00 am. They had a large snowstorm the week before we got there. Also, the altitude is pretty high. It is about 8000-9000 feet. It is probably warmer now but not much. We left temps in the 90s with humidity about the same so it was very refreshing. When we got home we stepped out of the airport at Dulles at about 1:00 am and it was like jumping into a sauna.
Allow a lot of time to see Yellowstone. It is a huge park. There are a lot of must sees and it takes a good amount of time to get from one location to another. Keep your eyes peeled for wildlife - there is a lot of it around (and some is in the road). The animals are wild so keep your distance and mothers are protective - don't get between a mother and her young. Some people are under the impression that the bison are like cows but they can run 35 mph and jump 6 feet, and they weigh a ton. If you keep your distance they are fine. Saw a van load of Japanese tourists run out into a field full of bison and got about ten feet from one and then were making noises to get it to lift its head. I was ready for my "when animals attack" photo sequence but, luckily for them, it didn't charge.
We drove back to Jackson at night both days we went to Yellowstone and the elk stand in the road just like the deer do around here. They weigh up to 800 pounds so you don't want to hit one. If you see cars on the side of the road it usually means there is an animal (or animals) worth seeing. If you see 100-200 cars it is probably a bear. If you have extra sets of eyes it makes it easier to spot the wildlife. Oftentimes it is just a slight movement off to the side that clues you in that something is foraging in the brush.
On the road between Norris and Mammoth on the left there are pull-offs to see moose. Did not see any moose but saw a ton of elk. Just before sundown a herd of about 75 or more came out to graze in the field. Also on the right as you head out to the Canyon from Norris there is a big field and saw over 50 elk there just at sundown. Just like fish, the herds of animals seem to become more active and come out just at sundown.
The canyon and falls are a definite "must see". Also, the bubbling pots and bright blue pools are something you will not see anywhere else. Cogitator covered the geysers pretty well but I will just add that there are a lot of them but most erupt at very infrequent intervals - Many once a day and some years between eruptions. Old faithful goes up every couple of hours, as do a couple of others. Definitely worth seeing a few of them and check cogitator's recommendations. Stop in to see the Old Faithful Inn right at Old Faithful. It is very unique.
Just North of Old Faithful is Biscuit Basin. It has very colorful pools and is worth seeing. Just North of there is Grand Prismatic Spring. Also worth seeing. Further up on the right is Fountain Paint Pots. It is a couple of mile hike and a steep walk at the end but worth it. Bubbling pools of white mud. Allow at least an hour for each of these three spots. (the same goes for just about anything you want to stop and look at). Norris Geyser basin is also worth seeing. Lost of geysers and crystal blue pools. Also bubbling mud pots.
Allow a good part of a day to see the canyon, especially if you plan to do any hiking. We did not do too much hiking. To get to the lower part of the canyon by the falls you go down about 600 steps which means you have to walk back up about 600 steps. I was carrying about 60 pounds of camera equipment and was not used to the altitude. Even still, what I was able to see without doing the extra hiking was spectacular.
Part of the loop is under construction so there can be long delays (part between the canyon and the lake if my memory serves me). The next leg between the canyon and the falls is closed. It is not a big deal but it means you have to backtrack. I think you can still drive on parts of it - you just can't follow it all the way through.
If you have the time, take a day and see the Tetons. The pass to get into Yellowstone gets you into Teton National Park as well. It abuts Yellowstone at the South Entrance. It is 58 miles from Jackson to the South gate of Yellowstone so to get to the Tetons it is about half that (maybe a little more). The mountains in Teton are incredible and there is a good amount of Moose there. Also saw a lot of antelope. If you do go to Teton be aware that they are doing construction on the road in Teton just South of the park. They have a "stop-slow" guy there and he lets about a mile or two of cars through each time so you may be waiting for half an hour to get by.
If you want info on Teton I can help you out. We spent the majority of our time there and got good advice from some of the locals.
If you plan on taking pictures of animals, bring along a long telephoto lens if you can. Bring binoculars if you can as well. I didn't and my wife and I had to switch back and forth looking through the camera lens. I also found using a polarizing filter was essential in many cases because of the bright sunlight. Bright, sunny days were best for seeing the colored pools. The better sun was in the mornings but that can also depend on the general weather pattern that day. I put some of my pictures on the web at WebShots
Also, the National Parks Service has a ton of info on their website including interactive maps with photos of most of the natural phenomena.
This is just a small piece of what is there. Most people spend about 6 hours there and just do the loop. You really need to devote several days to take it all in. I probably overlooked 80 percent of the park when we went, just saw some of the things you can see from the road. The parts along the road probably only cover about 10 percent of the park so I only saw 20 percent of 10 percent. It is overwhelming. Try to plan it out a little if possible.
This was sort of our five year anniversary / second honeymoon and my wife (who had never been there) thinks we should do it for our tenth. (I'd like to do it for our sixth but I think she has other ideas for in between like places with spas and shopping).
It will definitely be a trip you will never forget.
We are actually staying in West Yellowstone and will probably spend 4+ days in Yellowstone and maybe a good part of a day in the Tetons with another day possibly in the Craters of the Moon N.P. off to the west.
I had trouble viewing your pictures. You might have linked a page that is for your own personal editing. I have my webshots account HERE. I doubt my picture quality will compare with yours. ValerieUSA, our new unofficial chapter photographer does a much better job as can be seen on this thread.