live hotmail with your own domain
yeah, i've never actually been a fan of hotmail, but since they've started with the live domains, i kinda changed my mind. you change your mx record for your domain to point to hotmail and then you can use that for as many mailboxes for your domain as you like (each with 2gb), also you get a little advert you can post on your website and users can signup for free to a 2gb mailbox with your domain name. pretty nifty i thought.
as for the interface, i've been part of the beta for months now and there was one stage when there were issues with scrolling, but they've been resolved it seems. the integration with msn is also very nice for receiving alerts on new mail messages, contacts, etc...