With the rollout of GitHub Pages, why not show the world that you collaborate on GitHub? I’ve prepared these ribbons that you can overlay on your site by copying and pasting the appropriate snippet into your site’s HTML. Make sure to change the URL in the link to contain your username instead of “you”.
If you’re not satisfied with one of the colors here, I’ve provided the PSD files (MIT licensed). Feel free to modify as you please. The font being used is Collegiate.