Since the DOCTYPE I have been using on this site is labeled "XHTML 1.0 Transitional," I thought it would be appropriate to actually make the transition.
The site is now XHTML 1.1 compliant (with the exception of the pop-up comment posts that are built in to Movable Type--I'll edit those someday).
I've been working back through old posts, correcting any HTML errors that I may have made (mostly having to do with a use of <blockquote> and <ul> that conflicted with Movable Type's auto-line-break paragraph mechanism). Fun fun.