This is one of my favorite live sites, and I've been waiting to blog about for a few weeks.
If you have a custom domain (like me) and you want to give out free hosted email accounts to family members and friends (in my case, shahine.com has a few accounts that my family uses) go to http://domains.live.com/.
Windows Live Custom Domains allows you to basically point your MX record to us (Windows Live) and get free Windows Live Mail accounts, messenger accounts, and well anything you can use a passport for. No longer are any @hotmail.com or @msn.com domains necessary. You can get or use your own domain, and then enable all these great services. Plus you maintain control of your domain, so you can have your web site hosted elsewhere, etc. Only your email services are hosted by us. You can also kick people out of your domain, sign up for premium features in our network (like extra storage accounts, outlook live, msn premium etc).
Oh, did I mention, the service is FREE. All you need is access to change your DNS records. Once you do that you can create accounts and give them out for folks to start using.