Atlassian JIRA - Atlassian JIRA is a project management and tracking software for the business users, developers, programmers, etc.
Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.
Assembla - Integrated, on-demand tools to build software faster, with less stress. Get started for free and find out why over 800,000 users trust Assembla.
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.
Redmine - Flexible project management web application
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.