One more great addition to Hotmail! This is a step beyond the already available Hotmail feature to add a plus sign ('+') and a descriptive word to the first part of your email address.
QuoteStarting today, you can add up to five aliases per year (http://mail.live.com/?rru=createalias) to your Hotmail account, up to fifteen aliases in total, all designed to make it a lot easier to organize different types of email and personas in one Hotmail inbox without having to give out your primary email address if you don't want to.
From http://windowsteamblog.com/windows_live/b/windowslive/archive/2011/02/03/hotmail-delivers-aliases-to-help-you-manage-and-secure-your-email-account.aspx