Its really not worth mentioning with all these awesome projects in the comments, but i created a Pure CSS slider, which i think was away for me to show people my level in CSS. Plus it got a lot of stars on github haha. https://github.com/Elitewares/CSS3-Slider
Of course it's worth mentioning :) Even small projects are worth posting, like this recent one by Holman: https://github.com/tholman/github-corners