Signature.email - A powerful visual drag and drop email signature generator paired with the easiest way to maintain consistency for your whole team.
SignatureSatori - A Solution for central e-mail signature management for Google Apps.
WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.
MySigMail - UI email signature generator on GitHub
NEWOLDSTAMP - Email signature generator
Signature Hound - Email signatures made easy.