It's called ABC notation. See the ABC Music Project: http://abc.sourceforge.net/standard/

You can convert ABC notation to MIDIs or PDF scores using one of the online converters:
At Concertina.net
At folkinfo.org

There's probably a Permathread explaining ABC and the converters, since the notation is used quite a bit at Mudcat Café.

If you're on a Mac, consider getting the Barfly application (freeware/shareware, and well worth the price).