For the unenlightened, Git is a distributed version control system that’s recently taken the software development world by storm. It’s what we use to manage all of our source code at 37signals. GitHub is an online service providing Git repository hosting and collaboration tools (we featured them recently on the Product Blog).
Rails, Capistrano, and Prototype are already hosted on Github, and we’re going to be releasing some of our internal libraries and plugins there as well. Feel free to follow, fork, clone, and contribute!