Well, I spent the last couple hours writing a quick Java -> Jabber -> BlogToaster app. It seems like it works (I'm going to bed now and I haven't tested it thoroughly). Try it by sending a message to firstname.lastname@example.org. It will say the user is offline because my presence code is messed up, but you should get a response if you type a message. It works just like BlogToaster, it just looks at Weblogs.com every few minutes to see what's been updated, then notifies those users who've registered for those blogs.
You can also get the source code and jar here. You'll need Java 1.2 at least to run it. Just go into the bin directory and type "run jabber.com username password" or whatever your jabber server happens to be.
Going to bed. It's like 5 a.m. and I have to work tomorrow... UGH!