FYI - In case you guys don't read the blogs.
Major Nelson's just announced that Microsoft's Xbox Live service will be undergoing its scheduled maintenance on Tuesday, March 27, from 0000 to 1400 PT. The maintenance will also include Xbox.com and the Xbox forums. All three services will be unavailable at the aforementioned times.
According to the Major, the scheduled maintenance is "purely back end work" that's been scheduled "months ago". Details on what the maintenance will bring to Xbox Live users have yet to be revealed, so we'll just have to wait until it's done. Major Nelson did say however that it's not a dashboard update or anything of the sort. Apparently, the dashboard update will happen "later this Spring."
There you have it, folks. You still have a few days left to plan out what you'll be doing during the time that the service is out.