Sortd - Rated the #1 App for Gmail
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.
KanbanMail - A Kanban board for your emails.
Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.
Corrello - Dashboards for agile teams using Trello
Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.