From Webmonkey’s review:

If you don’t have a .Mac account, you can still publish a site with iWeb. If you choose the “Export” option in the File menu, your site will be packaged up and placed in a folder on your desktop. From there, you can upload all of your content to a hosted domain via FTP. iWeb doesn’t have any built-in FTP client, so you have to resort to using a third-party client like Transmit or Fetch if you don’t have a .Mac account.

Also, non-.Mac users are required to enter a URL for their site when it’s exported, or else some of the RSS functionality is lost. Also, the fancy Ajax slideshow won’t work outside of the .Mac servers. You can still publish a photo slideshow and post it to your independently hosted site, but you’ll get the older .Mac slideshow container without the Ajax controls and without the sleek special effects.

So that’s great news. Although a .Mac account is required for a few features, most of the functionality of iWeb will still be usable to those without an account. .Mac is far too expensive in my opinion - if it was around half the price I’d create an account in a snap, but as it is, it’s just a little too much for the meagre 1gb diskspace offered etc.