WARNING: THIS IS OUT OF DATE - MAJOR UPDATES ARE AVAILABLE FROM THE MAIN dumbcraft tree. https://github.com/cnlohr/avrcraft - there is actually an ESP8266 port there!!!
My first stab at a Minecraft-enabled firmware for the ESP8266
P.S. It works.
Video is here: http://www.youtube.com/watch?v=R1zx0xV0pWw&list=UUG7yIWtVwcENg_ZS-nahg5g