Several years back I found a list of Idaho Hot Springs from the USGS, or such. A few months ago, I chopped off the bottom of the list (hot springs instead of warm springs) and formatted it for my GPS. In the mean time, I'd tried GoogleEarth when it was released, but did not have a GPS at the time. Since then I've acquired another GPS and signed up for GoogleEarthPlus to be able to import GPS data. If you have GoogleEarth, attached to this story is a file with the majority of Idaho's hotsprings (you can use the file with the free version of GoogleEarth). And here is a page about U.S. geothermal Activity. And here is a website dedicated to Idaho Geothermal activity.