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.

HelpScout - Help Scout is a simple, straightforward way to provide excellent support

Instagantt - Instagantt is a powerful and intuitive Gantt chart tool to enable teams to plan, manage and visualize their projects easily. Manage your schedules, tasks, timelines, and workload like a Pro. Try it for free.

Labidesk - LabiDesk is all-in-one help desk software for Omni Channel Support: Shared Email Inbox, Ticketing System, HelpWidget, Knowledge Base, Live Chat. Assist, Engage and Sell to your customers!

Manifold - Manifold GIS is a combination of mapping, CAD, DBMS and image processing.

Halp - Slack-first ticketing for internal helpdesk