According to this, Proudmoore is the first server to reach phase 3 in the Shattered Sun Offensive. Cenarius is a very close second, at 99% right now. This came up in guild chat the other day, how hard it must be to do these dailies on a PvP server. For the curious, the first PvP server on the list is Blackrock, at #12 (87%). The second is Jubei'Thos, a huge jump away at #34 (77%). In last place right now is Blood Furnace, sitting at #224, with 2% in to phase 2.

For the theorycrafters out there, the brains over at Elitist Jerks are starting their Think Tank project. It will likely be a very valuable resource, so head on over and check it out, if you have the chops.