Sortd - Rated the #1 App for Gmail
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
KanbanMail - A Kanban board for your emails.
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!
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.
ProWorkflow - Simple Project Management Software. Schedule and Track Time Easily Using Timesheets, Try ProWorkflow for Free Now!