In true Microsoft style, the feature is impossible to find but if you hover over the "Inbox" link in Hotmail, a little gear icon will appear and you can create a new alias that way.
Aside from all the weird, tasteless, mind-numbingly awful stuff you can now secretly subscribe to, Microsoft's blog post points out a more mundane use.
Let's say you're in the market for a new car. There are a bunch of websites that will email you price quotes, sales alerts, etc. During your car search, these messages are helpful, but once you're done, they become clutter that can be difficult to stop. By using an alias on these websites instead of your main email address, you can avoid this. And when you're done, just turn the alias off, ensuring future unwanted messages that are sent to that alias don't land in your inbox.
Feb 10, 2011
Hotmail now has disposable e-mail addresses
Microsoft's Hotmail service has added a new feature that lets you use an e-mail alias completely separate from your regular e-mail address that funnels directly into your main Hotmail account.