Top Ten Things To See in Yellowstone (from Yellowstone.Net)

Top Ten Map
Old Faithful 1. Old Faithful / Upper Geyser Basin
The name says it all. Old Faithful is the most popular attraction in Yellowstone, and everyone who visits for the first time should watch this most famous of geysers erupt. Although neither the highest or most regular geyser in the Park, it is spectacular. Also, take an hour or two to walk around the boardwalks and visit some of the many other geysers in the Upper Geyser Basin, such as Castle, Grotto, Riverside and Daisy. And be sure to take the 1.4 mile walk to Morning Glory Pool, one of the most colorful thermal features in all of Yellowstone. In addition, be sure to visit the Old Faithful Inn, which is the single most impressive human structure in Yellowstone. And finally, bison and elk can oftentimes be spotted grazing in the area.
Grand Canyon 2. Grand Canyon of the Yellowstone
Yellowstone's Grand Canyon may not be as big as the Grand Canyon in Arizona, but it is nonetheless breathtaking. The Lower Falls of the Grand Canyon, at 308 feet high, is one of the most photographed features in all of Yellowstone. There are numerous vantage points on both the North and South sides of the Canyon, and we recommend that you take the time to view the Canyon from both sides. Also, be certain to take the 3/8 mile (one way) hike down to the edge of the Lower Falls. The experience at the lip of the falls is breathtaking.
Hayden Valley 3. Hayden Valley
This valley, centrally located in Yellowstone, is the first place to go to see wildlife in Yellowstone. As you drive along this beautiful, broad valley you are likely to see herds of bison, perhaps some elk, and the occasional grizzly bear. The valley also offers a great view of the Yellowstone River.
Mammoth Springs 4. Mammoth Hot Springs
This is Park headquarters and it radiates history, featuring some of the oldest buildings in the Park, including structures from the days when the U.S. Army was managing Yellowstone. Be sure to drop by the Visitor's Center and allow enough time to watch a film, browse the history exhibit, and walk through the upstairs wildlife museum. In addition, Mammoth Hot Springs Terrace, although the thermal activity is slowing dying, is quite magnificent, and the Terrace drive is a must. Finally, be sure to look for the seemingly ever-present elk grazing on the green lawns of Mammoth Village.
Yellowstone Lake 5. Yellowstone Lake
This is the largest high-altitude lake in the lower 48 states, and it is breathtaking in grandeur. As you follow the long shoreline both east and north, you will see snow-capped mountains rising across the lake. On windy days, ocean-like waves break onto the shore. Be sure to visit Lake Village and walk through the Hotel. You might also want to sit on the porch of Lake Lodge and take in the view
Norris Geyser Basin 6. Norris Geyser Basin
One of Yellowstone's most popular geyser basins, Norris is home to Echinus (one of the Park's most popular geysers) and Steamboat (the world's largest geyser, which last erupted on May 2, 2000). In addition, there are several miles of boardwalks from which you can explore dozens of multi-colored thermal features. Finally, elk and the occasional bison can sometimes be spotted in the area.
Lamar Valley 7. Lamar Valley
This wide, expansive valley is home to bison, elk, coyote, grizzly and wolf. Bison and elk are readily visible, and coyotes can oftentimes be spotted. Visitors who are willing to rise early in the morning or wait up until dusk also may have the opportunity to see bears and wolves. The valley is rather remotely located in the northeast corner of the Park, otherwise it would receive a higher ranking in our Top Ten.
Tower Falls 8. Tower Falls
This is the second most popular waterfall in Yellowstone behind the Lower Falls of the Grand Canyon. The waterfall is located behind the General Store. A short walk will take you to an overlook, but we also recommend you take the short-but-steep hike down to the base of the waterfall.
Lower Geyser Basin 9. Lower Geyser Basin
This geyser basin features regularly-erupting geysers, beautiful thermal pools, and a fascinating mud pool which often strikes visitors as something from another world.
West Thumb 10. West Thumb Geyser Basin -- This geyser basin features some interesting thermal features, including several which are in Yellowstone Lake itself. It also offers a good view of the Lake.