I just picked up the free version of Bryce7 the other day, been using 5 for awhile - basically you can import existing free online models and photo realistic textures or make your own and combine them into a scene for a single image or animation sequence! It's a pretty creative environment really & 7 has a bunch more stuff in it, there are also tons of tutorials and art groups online for it - many here on DA!
I have seen a lot of great works done in Bryce.
But it's cool and well done.