Stacy at Hosting Matters sends this PSA:
We're having a power issue that's affecting one of ourcabinets housing multiple servers. Most servers are unaffected but we just want to let folks know it's being worked on and should be resolved very shortly.
If your blog or any of your favorite blogs are inaccessible right now, that is most likely the reason.
If you know HM like I know HM, then you know the problem will be resolved as fast as humanly possible.
Here's the link
to the emergency forums, should you need it.
[On an unrelated note, blogrolling has been out most of the day. I suggest that if you are running a blogrolling script on your site, you take it out until the service comes back, or your site will be very slow to load]
Update: Looks like everything is up and running again!