I was able to spend some time in the Norris Geyser Basin on Thursday. It is the hottest geyser basin in Yellowstone and is the one that is most prone to change. Those changes were quite dramatic in the summer of 2003 and the Basin had to be closed to visitors.
Up till 2003 the path with through the area in the picture below. There was one small geyser near the path, but it generally was quiet there. But in 2003 the ground got incredibly hot and some spouters actually came up right under the boardwalk and around it. They had to tear out the path and rebuild it around the edge for quite a distance.
If you go to Yellowstone, look for people who know a lot about geysers (often called geyser gazers- they won't always be Park employees). They'll usually have sturdy backpacks and sometimes be carrying some type of chair to sit on. They might be waiting for a boring-looking geyser that everyone else passes. When you see them, stop and ask questions. They love to talk about geysers and can tell you interesting things (one told me about the new geysers in Norris) or let you know what geysers in the area might be erupting if you wait for a few minutes.