Sortd - Rated the #1 App for Gmail
KanbanMail - A Kanban board for your emails.
Gmail Add-ons - Work with your favorite business apps directly in Gmail
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
Asana for Gmail - Turn emails into tasks without leaving your Gmail inbox
Drag for Gmail - Transform Gmail into organized To Do lists (like Trello)