It looks like after being pulled several times, the official service pack numero tres is gets to see the light of day and is now available on the Microsoft website. It looks dated to be the latest version as well, so grab it before Microsoft has another change of heart.
As quoted from the Microsoft site:
Windows XP Service Pack 3 (SP3) includes all previously released updates for the operating system. This update also includes a small number of new functionalities, which do not significantly change customers' experience with the operating system.We always recommend getting the latest service packs and fixes to keep those security holes blocked from those evil hackers that live under your neighbor's basement.