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.

Mailmeteor - Send hundreds of personalized emails with Gmail.

Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.

GMass - GMass allows you to easily schedule emails, send out mass emails and mail merge campaigns and more with Gmail! Click here to learn about more features!

Perfect Wiki - Build and organize your knowledge base of company resources without switching between workspaces

Interseller - Interseller helps find contact information, reach out to them with email automation and syncs it all into your database.