GitHub (http://github.com) is the largest git-hosting site, with more than 150,000 public repositories. It provides both free hosting for public projects and paid options for private projects. With a custom web interface that includes wiki hosting, issue tracking, and an emphasis on social networking of project developers, it’s a great place to find new code and collaborate on existing libraries. You can sign up for a free account at http://github.com. When you do that, you can copy and modify the book repository or create your own open-source iOS projects to share with others.