I've been meaning to watch this video since August. It perfectly describes all the things that make Second Life so cool. Additionally, it dives deep into the nerdery of running a home-brew state-based scripting language on the Mono VM. Sweet!
Nerds! Start at the 45 minute mark if you already know about Second Life and love demos with plenty of bytecode.
Mom, Arts students, Ms. Laplante, everyone else: Watch the first half; that's all the juicy Second Life stuff.