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.
Unfuddle - Unfuddle is a secure, hosted project management solution for software development teams.
Hygger - Hygger - is an Agile project management tool with built-in prioritization.
Backlog - A cloud-based project management app for developers and their teams.
Codegiant - Codegiant - Issue tracking, git repositories, continuous integration and documentation in a single platform.
TaskBlast - Versatile and easy to use Project Management tool to get all team members involved.