Email Privacy Protector - Check the presence of email ids on your webpages using Email Privacy Checker tool and protect yourself from email spammers.
Canned Emails - A minimal site with prewritten emails
PixelBlock - Block email open tracking inside of Gmail
analyze.email - Test the spam-y-ness of your emails
Ugly Email for FireFox - Get back your email privacy, block email tracking
TestSubject - Test how your email subject line displays on mobile devices.