To host here, you need to pay the monthly hosting fee, which is about $10/mo. Your seven domains are $9.95 per year each, and that lets you point your domains at the WordPress.com hosting site. I like hosting here because it gives me full access (shell, files, etc) to my account.
Since you mention iWeb, that’d require the above mentioned Full Hosting package with the monthly fee.
If you’re going the Full Hosting route, I’d suggest that you host your WordPress blogs over here as well. I have a handful of them here and they’re quite easy to manage, thanks to WordPress’ built-in update mechanism. I started mine here with the One-Click Advanced installs, then used the WordPress admin interface to keep everything up to date.