Trello is a collaboration tool that organizes your projects into boards. In one glance, Trello tells you what's being worked on, who's working on what, and where something is in a process.
Asana is the easiest way for teams to track their work. From tasks and projects to conversations and dashboards, Asana enables teams to move work from start to finish--and get results. Available at asana.com and on iOS & Android.
Capture the knowledge that's too often lost in email inboxes and shared network drives in Confluence instead – where it's easy to find, use, and update.
Redmine is a flexible project management web application. Written using the Ruby on Rails framework, it is cross-platform and cross-database.
Bugzilla is a "Defect Tracking System" or "Bug-Tracking System". Defect Tracking Systems allow individual or groups of developers to keep track of outstanding bugs in their product effectively. Most commercial defect-tracking software vendors charge enormous licensing fees. Despite being "free", Bugzilla has many features its expensive counterparts lack.