In case you didn't know, Bryan Fink of BeerRiot fame has created a Facebook library for Erlang called erlang2facebook. You can get it from http://code.google.com/p/erlang2facebook/. It is bundled with a complete Hello World Facebook app that is built with ErlyWeb, so you can hit the ground running with your Erlang Facebook development.
I can think of some fun projects to build with this library. If you're going to use it to build an app, please let me know!