Ask HN: Cool Useful GitHub Repos?

And when you're done either smiling or shaking your head,

Cool: - https://github.com/c3d/xl - maybe smalltalk xstreams

I''m going to bed.

Does it have to be from GitHub, or are you also interested in cool projects that may be hosted somewhere else?

It's gone, what was it?

See forks.

Omg you just gave me the exact tool I needed Ty.

In Addition to suggestions here, check http://github.com/trending for interesting repos