You can use the dotMac personal domain service without having to actually use iWeb ’08. To do so, simply follow the instructions on the Right about using Personal Domains. Once you’ve got as far as setting up your domain with your registrar, you can use any software you wish (RapidWeaver, Sandvox, Hand coding even) to create your own site.
Simply navigate to your iDisk and make sure you place all your html files in the following folder: iDisk » Web » Sites. Anything in this Sites folder will be used by the personal domain service. I’ve made a simple ‘hello world’ HTML file and placed it in the Sites folder. As long as there is at least an index.html file there, it works correctly.