Favorite Mineral Springs and Hot Tub Places [TheOldNet][Direct] -
Mostly covers thermal delights in California, and touches on other western U.S. States; especially useful is the "places to be avoided" section. By Ellen Guon Beeman.
Hot Springs in the U.S. [TheOldNet][Direct] -
Data from the U.S. National Geophysical Data Center. Includes coordinate location and surface temperature in fahrenheit and celsius.
Idaho Hiking and Hot Springs [TheOldNet][Direct] -
Helpful for those with thermal wanderlust. Includes information on how to get to backcountry springs and provides ratings of different locations.