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.
All disposable email address services provide this basic functionality, but some have other neat features that make life with email less spam and more fun.
(Updated May 2011)
Spamex provides a solid, useful, and almost feature-complete disposable email address service.
Before you choke on all that spam, try the feature-rich and flexible disposable email addresses from Spamgourmet for protection.
E4ward.com is a down-to-earth and very useful disposable email service that makes it easy to prevent spam to your real email address with easily erasable aliases. You can use your own domain with E4ward.com, but address masking in your replies is a bit cumbersome and auto-expiring aliases are not offered.
GishPuppy is a disposable email address service that shines with simplicity and functionality. Unfortunately, GishPuppy's functionality does not encompass replacing your real email address with the appropriate alias in replies.
Mailinator lets you use any email address @mailinator.com and pick up the mail at their site. Since there's no connection to your real address, you sure won't get spam from using Mailinator addresses. Keep in mind that all mail sent to Mailinator is made public.
Yahoo! Mail Classic is a comfortable, reliable and secure email service with unlimited storage. A pretty good spam filter (including disposable email addresses) keeps the junk out.
Note that disposable addresses are deleted when you cancel your Yahoo! Mail Plus account.