Minecraft 1.5 has been released!
Minecraft 1.5, The Redstone Update, was released today. There is already a planned 1.5.1 update in the work.
Given that we're using Bukkit, we'll be staying behind on 1.4.7 until a new beta release of craftbukkit comes out.
As in the past, if you've already upgraded your Minecraft client and then connect to the library server, you'll be told that our server is outdated and then disconnected.
Tools such as Minecraft Version Changer will allow you to roll back your client to connect with the library's server.