I did something similar to Americorps, but it was all in the National Parks. It's called SCC, and I found out about it through Americorps. They stationed me in Badlands National Park, where I gave interpretational talks about prairie dog towns, fossils, and geology. You live on the park with all the other rangers and stuff, it was really cool.
Hmm... ok, turns out I actually have nothing to say about Americorps itself, except that I found out about another program through it. That doesn't really answer your question.
Carry on then!