Parrot
Excellent article about Parrot, by Allison Randal.
Parrotâs record for a language implementation was a conference session where the speaker implemented the basics of the LOLCODE language from scratch as a live demonstration. It was a 5-minute lighting talk.
I have to get the time to implement a DSL for something on top of Parrot, to see how it works. Right now I only compile Parrot to run Rakudo.