Have fun!

I recommend you start with the Nock tutorial:

http://www.urbit.org/2013/08/22/Chapter-2-nock.html

The build instructions in this file are out of date, use the ones from the Arvo chapter. Also, probably the best short overview is the header comment in the Hoon compiler:

https://github.com/urbit/urbit/blob/master/urb/zod/arvo/hoon...

Also don't miss the video: https://vimeo.com/75312418