This looks a lot like Haml: http://haml.hamptoncatlin.com/

Haml also happens to have a tutorial, documentation, and downloadable source code.

If you want to try Haml online, check http://lab.hamptoncatlin.com/

I came here to say pretty much the same comment, haml is awesome (I'd much rather use it in a project than something equivilant to generate xhtml [sass is nice too :P]).