Check it out; it's part of the "Sacred Texts Online Gallery" of the British Library.
This Psalter is apparently very famous for its depictions of "ordinary life" in medieval England - and some of the illustrations are indeed pretty great. You can zoom in and out of many of these images, too, and see them very close, if you like.
Here are a couple of examples of the illustrations, from Wikimedia Commons:
What a great thing; I'm sure there are other manuscripts at this site worth exploring. Go to this page, for instance, and you'll see a link to the Sherborne Missal, which looks to be interesting; it's a Flash movie, and you can hold a little Flash magnifying glass over the pages to see them closer. Gotta love it! And the Lindisfarne Gospels can be found here.
There's also an entire website devoted to the Luttrell Psalter, as well as a "Luttrell family" genealogy site with a Psalter section.
Busy, busy, busy!