NOTE: I'm not a SEO guy. If this post used wrong wordings, sorry for that. And, I'm not a native English speaker, don't blame my English writing :P And, I don't know whether someone has shared something similar :)
I have several pet projects hosted on github. And, I observed that Google give pretty high ranking to github repository. If a github repository has a homepage, that homepage will get benefits as well.
Thus, I carried out an experiment at https://github.com/mrkschan/github-seo-effect. I used the search terms "Github SEO effect" as the repository name and set the homepage that links to my blog post at http://mrkschan.blogspot.hk/2013/03/github-seo-effect.html
The result is pretty amazing. Here is a Google search result before I carried out the experiment (I was using Chromium private browsing, with links set to use "gl=us").
After a few days that I set the homepage to the blog post, the result becomes the following screencap.
BTW, shall we abuse Github for SEO purpose? Try your search here: http://www.google.com/search?gl=us&q=github+seo+effect