I heard that some people were asking invites for Windows Live Mail and I thought that this needed a little bit of clarification.
Microsoft is not going the Gmail way by allowing their users to distribute invitations. We all agree that this has largely contributed to the hype of Gmail (+ the 1GB of storage), but I think that this is not really fair. Microsoft has an open beta-test of their new interface for hotmail, which means that you can sign up for it.
Microsoft hasn't made things easy (who said like usual ?) but maybe it's intentional as they might not be able to handle large server loads, they're Microsoft after all. To get your invite, go to the Windows Live Mail sign up page and enter your email address. It goes without saying that you need a hotmail or msn account to be able to use the beta service and that Internet Explorer is strongly advised if you want to take advantage of the new possibilities of Windows Live Mail
Stuart has written a nice review of this webmail service
I hope it helped