I wrote an article on collision detection for Build New Games, and it's live! Check it out here.

For this article, I wrote a demo engine, and the whole thing is on Github for easy perusing. Something I discovered is that if you create a project/repo on Github, and then only push the gh-pages branch, it is used as the default automatically, and you never have to worry about committing/syncing between master and gh-pages. NEAT.