Craftbukkit build 2317 AKA 1.3.1-R1.0 (which is compatible with Minecraft 1.3.1) has been released. We have installed it on all of the basic game servers. If you have a VPS or dedicated game server please open a support ticket to have this version installed.
As with all new builds of Minecraft/Craftbukkit backup your world and nether before changing version.
Please let us know if you find any plugins that do not work with build 2317.