Actually there is some real weirdness going on.
I'm running Leopard, and have iWeb, and the System Preferences are a .Mac panel. In iWeb, it's all about .Mac.
I don't actually have .Mac, but I managed to register for a free trial of MobileMe today when MobileMe was working.
Now, there doesn't seem to be any system update to perform, but iWeb is still saying .Mac. I created a sample web page and uploaded to .Mac, and it worked with my MobileMe trial login. I'm also logged in to MobileMe through my .Mac system preference panel, and it shows the correct details (ie, trial account, expires in 60 days).
I can visit my test webpage by going to the .Mac URL, but not to what I've guessed is the equivalent .me.com URL.
There doesn't seem to be any way to update or migrate anything to MobileMe, although to be honest, I can't log in to the account settings page.
I'm assuming there will be some update to iWeb to integrate with MobileMe?