Meetingbird for Gmail - View your calendar and schedule meetings right from 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.
Kin Calendar - The simple and connected calendar
Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.
Calendly for Chrome - Schedule meetings without leaving your inbox
Corrello - Dashboards for agile teams using Trello