As many have already said, Github just keeps delivering quality, well-conceived and well-integrated updates. I hope they keep coming.
Now for my shameless plug:
If you use Gist as a means to share web-related snippets, you might be amazed by the Plunker editor (http://plnkr.co/edit/). It was inspired by Gist, but will let you actually 'run' your code (and will do some other cool stuff like real-time collaboration, previewing and linting). This tool has become quite popular in the AngularJS community and I hope to see more groups get on board in the future!