In my Monday Morning Musings post this week I noted that XP SP 3 was supposed to be deployed yesterday. Apparently there was an issue with machines running something called Microsoft Dynamics RMS (Retail Management System) software and Microsoft has delayed deployment until it can add filtering to the updates. This same problem with RMS applies to Vista SP1 as well.
If you go read all about it at Windows IT Pro, you can find a link to get the download.