Thanks, all, for the compliments. I've been registered at CGSociety for a while, but I've only this week started to actually lurk there actively. It just gets so much traffic that it's hard to sift out stuff that I want to read.
Another good site specifically for mattes is http://www.mattepainting.org . Again, it's another forum that I registered on a while ago but only recently started reading regularly.
And http://www.conceptart.org is useful, too.
WM: That's a nice clear tutorial for getting started. It does have a couple of issues, though, and I think pointing to them here might help anyone who happens to be working on a matte painting.
First, the house has some fairly extreme lens distortion. Notice how the second story bends to the right. Photoshop can fix that with the Lens Correction filter (Filters > Distort > Lens Correction). You want to make sure that the matte will fit nicely behind your primary photography, so you don't want any obvious lens distortion unless it needs to match up with similar distortions from your footage. It's best, though, to start with an undistorted image and let the compositor decide if the painting needs to be reshaped later on.
The second thing is that lightning. Since a matte painting is intended to be composited with live footage, you don't want to include anything that is supposed to be moving. Lightning, water, animals, and fireflies should be left out. Caveat to that: It is common to show water in a matte that stands alone, but it will almost always be left out of the image handed off to the compositors.
I'm in a compositing class right now, and those were some of the things that were common errors in the paintings we critiqued this week.
edit: Oh, and the handle is the Anglo-Saxon version of Jormungandr, the Miðgaard Serpent of Norse Mythology ("sormr" being "serpent" in several Germanic languages), the force of uncreation. Miðgaard itself is the "Middle Earth," or the world in which we live.