Mailinator - Any Inbox. Any Time.
Squat Captcha - The worst captcha ever! Forces you to do 10 squats
Guerrilla Mail - Guerrilla Mail is a web-based app that provides a disposable and anonymous email address. Users of the service are not required to set up an account in order to send or receive emails.
Humans Not Invited - CAPTCHA that filters out humans and only lets programs pass
Fake Mail Generator - Fake Mail Generator is the provider of free and temporary email addresses that you can use just like original one.
reCAPTCHA - reCAPTCHA is a free security service that protects your websites from spam and abuse.