Google is beta-testing the next logical step in Gmail's life cycle: providing hosted Gmail-based webmail for other domain names. At Gmail for your domain you can put your name on a list for a limited beta that'll provide 2GB of storage for each of your users plus a control panel for managing accounts, aliases, and mailing lists. No word on whether the service will eventually be subscription-based or AdSense-supported, but I'm guessing the latter.