It seems that Yellowstone National Park has been experiencing over 250 tremors over the past few days (which is a bit unusual for them). Its been about 70,000 since the volcano under the park exploded, so perhaps they are due (hmmm that sounds like a movie, a really bad movie). Apparently the magma is just about 3 to 4 feet below the surface, which is why there are so many geysers (like Old Faithful), hot springs, fumaroles (which you must admit is a great word! it actually means steam vents) and mudpots in the area.
To read more see: http://news.yahoo.com/s/ap/20081230/ap_on_sc/yellowstone_quakes_5
Yellowstone National Park has a WebCam on Old Faithful which is updated ever 30 seconds