If you give Web sites and new contacts a disposable email address instead of your real one, you can selectively disable a disposable address as soon as you get spam through it, but continue using all other aliases. Disposable email address services provide this basic functionality, but some have other neat features that make life with email less spam and more fun.

From About.com: Top 10 Disposable Email Address Services

From Listible.Com: 40 resources on Dispoable Email Services