A new service was added to the Windows Live Beta family today - Windows Live Custom Domains. The basic idea is that anyone with a domain can now point their MX record to the Live servers. What that means is that users can have Microsoft's servers hosting their own domain's email accounts for free. There's a restriction of 20 email accounts per domain, with each mailbox getting 250MB of space.
Try it out
or read about it over at Neowin