There's a great article describing the start of Erlang as a Prolog metainterpreter. It's very accessible, at least I can follow it with my month old Prolog knowledge and it's quite impressive to watch as the interpreter goes from nothing to basic concurrency in a few lines of code:

http://www.sics.se/~joe/pubs/prac_appl_prolog.ps‎

I'm taking a class that has some Prolog content and I've been playing with my own toy implementation. Fun stuff.