Holy crap, I awoke to find 200 spam comments scattered around my blog today! There's no easy way for me to get rid of them all. I'll at least clear up the main page though. I've tried adding "word verification" to the comments form, but the hack apparently doesn't work perfectly on Internet Explorer (if you have any problems, email me). I might end up having to change back to old fashioned Blogger comments. Anything to stop the flood of spam!
Update: It turns out the spammers were using the old Blogger pop-up comments link I'd left there before. I've now removed that link, so now the only way to comment is via the post-page comment form. Hopefully that'll be enough to keep the spammers out. (If not, I'll have to resort to old Blogger comments + word verification.)