Following the advice of another blogger frustrated with comment spam, I took five minutes to rename the comment submission script in Movable Type and make the necessary adjustments in the configuration script. It took the comment spam bots about 5 minutes to find out the new name of the script and begin posting crap to my site again. Gee, that worked like...not at all.
There's a hack called scode that enables requiring users to re-type a security code in order to post, but it's a pain in the ass to install. Maybe over the weekend.