There are 2 main advantages to GitHub:
- It uses git (duh!)
- It's a very "social" environment.
GitHub makes it very easy to make contributions to other people's code, and easy for them to integrate it back in. There are also lots and lots of cool post-commit hooks that they have built-in; for instance, when I commit to one of my repositories, an email is sent to my Google Groups announce list and a bot pops into the irc channel, gives a summary of the changes, and pops back out again. I know of at least one CI service that triggers on GitHub commits (or rather, pushes).
If you're planning on this being a fairly small, solo project, then you probably won't find most of GitHub's features to be that useful.