Some parts of Zune.net, including the Marketplace and (at least here) the ability to sign in to your Zune account from the Zune software are down as of this morning. A message posted on the Zune support page confirms the outage:
Status: You might be unable to browse, stream, download, or buy things at the Zune marketplace or on Zune.net. We’re working on the problem. Sorry for the inconvenience, and thanks for your patience. Sat 1/15/2011 5:28 AM Pacific Time
Now, if this were an Apple site, the twittersphere would be abuzz with rumors about something new and wonderful coming, but we’re afraid it’s just a plain ol’ outage. Hopefully things will be resolved soon.