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.
productboard - Beautiful and powerful product management.
Basecamp - A simple and elegant project management system.
Aha - Aha! is the new way to create visual product roadmaps. Web-based product management tools and roadmapping software for agile product managers.
Teamgantt - Intuitive project planning and collaboration. Beautiful Gantt charts, task-level communication, file sharing, resource management and more.
ProdPad - ProdPad helps your team gather ideas, surface the best ones and turn them into product specs, and then put it all on a product roadmap.