Jeb tweeted earlier that 1.3.1 has gone live and is out. Loads of new features like single-player being a self-hosted server and allowing LAN friends join SP games, Adventure Mode which doesn’t allow building or setting things on fire, Villager trading, made enchanting easier, automatic downloading of texture packs from servers (standard size only), added a multiplayer hardcore mode wherein players are banned upon death, fixed the creative mode pick-block key, and lots and lots more. For a full changelist, read this Reddit Post. Your client should update on it’s own.
Server news: We’ll be updating the server today but we will be wiping the map clean when Bukkit comes out for 1.3 so don’t make yourself too permanent of a house… I’ll also be opening up the whitelist to allow anyone that wishes to join to do so.