As mentioned late last night: If Xbox LIVE doesn't work for you today, there's good reason. Microsoft planned the outage for maintenance. "On Tuesday, June 16 beginning at 12:01 a.m. to 11:59 p.m. PDT (2009-06-16 0701 to 2009-06-17 0659 UTC) Xbox LIVE and Xbox.com will be offline for scheduled maintenance." In other news, PSN should be online, but it's still a bitter disappointment.
Yeah, just figured that one out. Finally picked up a 360 yesterday and was going to update the software so I can use it as my media center. Much to my disappointment it said I had an MTU failure over my WDS network. Two hours later I found out it wasn't me but Xbox Live!
Next time they are down, how about a lovely little sign that says "Hey, we are out to lunch, be back tomorrow!" instead of a networking error. Boneheads.