Ever balk at giving up your email address to an unseemly web site? Perhaps a "registration required" link you found over at Fleshbot? If you need to sign up for a web site with an email address, yet want to avoid a lifetime of spam involving horses and young girls, Mailinator's for you.
Pick any @mailinator.com email address you want - [email protected], even - and give it away. Then hit up Mailinator to check the public inbox, and any email you received will be there (and automatically deleted after a few hours). Great for one-off site registrations that you'll never want to hear from again.