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.
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.
Nifty - Manage projects, work, and communications in one place.
GanttPRO - GanttPRO is online Gantt chart software for project management. CEOs, project managers, and teams use it every day to solve project management challenges.
CAMPR - Open source project management tool with 16 modules
Gantt - Create beautiful Gantt charts