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.

Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.

Live Chat by Landbot - Live chat that combines chatbots with human chat

Corrello - Dashboards for agile teams using Trello

GoSquared Live Chat - Beautiful, simple, and free live chat for your website