reCAPTCHA Mailhide
http://www.google.com/recaptcha/mailhide/

Tired of spam? reCAPTCHA Mailhide helps you protect your inbox by asking people to solve a reCAPTCHA before they can view your email address. The reCAPTCHA can only be solved by humans, so this stops spammers from gaining access to your email address through automated programs. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog. This will be added to Privacy Resources Subject Tracer™ Information Blog. This will be added to Entrepreneurial Resources Subject Tracer™ Information Blog. This has been added to Internet Hoaxes Subject Tracer™ Information Blog.