I'm giving a tour of our backyard cavern this coming weekend, and I was just making some notes on the talk I'll be giving during the tour. Here is a link to one of the resources I've found for great cave information: http://www.nps.gov/archive/wica/Speleothems.htm
I have several major topics on my cave tour. The most important one is cave safety, but the most fun one is speleothems. Speleothems are the different types of formations found in caves. I try to include information on the science behind how speleothems are formed. Also, I remind everyone on the tour not to touch the formations because the oils in our skin create a barrier on the formations and prevent them from growing.
We have lots of awesome speleothems down in our family's backyard cavern. My very favorite one of all is called "cave popcorn." Check out the link below for a great picture of cave popcorn. http://www.nps.gov/wica/naturescience/speleothems-cave-popcorn.htm