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.
Elevio - Learn how elevio can help bring all your support channels into one, to provide the best support possible for your users
Basecamp - A simple and elegant project management system.
Lighthouse Desktop - KMS Lighthouse offers world class search technology, providing instant answers to questions to reduce time to accurate knowledge.
Teamgantt - Intuitive project planning and collaboration. Beautiful Gantt charts, task-level communication, file sharing, resource management and more.
Paldesk - Talk to visitors and customers over mutiple channels in real time. Drive all your web and social messages into one dashboard.