Dungeons and Dragons is working to get their game into more public libraries. You can take a look at their campaign at Dungeons & Dragons Roleplaying Game Library Web Page. If you get one of their printed flyers, you will see a quote from me advocating D&D in libraries.
I did D&D with a group of teens via the Teen Center we set up at a public library. It is one of the programs I am most proud of, because we turned a very negative situation with teens over-running the library each day into a positive one. Each afternoon, we converted the public meeting room into a teen center using a computer on a cart, lots of bean bags, and carts of very cool books, including D&D books and dice. It was a very popular space and one that resulted in a lot of positive things happening. D&D was at the center of bringing some of those teen boys in. It was a wonderful experience. I still miss some of those kids.