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.

WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.

Drag for Gmail - Transform Gmail into organized To Do lists (like Trello)

MySignature - MySignature is FREE Email Signature Generator that helps to create Professional Signatures for major email clients such as Outlook, Gmail...

KanbanMail - A Kanban board for your emails.

Exclaimer - Exclaimer is the industry's leading provider of email signature solutions, empowering businesses to unlock the potential of email as a key digital advertising channel.