I've added a new update. A trip last January to the caves in/around Great Basin National Park. Lehman's Caves National Monument is featured here and has decent photos of what can be seen in this gorgeous cave. I normally use a disposable camera for my pics and thus the quality isn't up to digital or even a full blown SLR but they work and a lot of them turn out quite nice.
If you've never seen Lehmans' I'd recommend it most highly. Take the long 90 minute tour over the 60 minute tour as you'll see more of the cave that way.
The guides are friendly and well trained Park specialists and knowledgeable about the caves' history and formations.
Click my signature to check 'em out!