If you're worried about the domain github.blog, be aware it's what blog.github.com redirects to. I really hate what's happened with TLDs, but at least this one is verifiable.
(I'm the open source PM at GitHub, for context... and yes I realize that's not directly verifiable from my sn here so feel free to tweet at me if you want to check: http://twitter.com/devonzuegel)