WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.
Sortd - Rated the #1 App for Gmail
NEWOLDSTAMP - Email signature generator
KanbanMail - A Kanban board for your emails.
Sigstr - Email signature marketing
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.