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.
Mantis Bug Tracker - Mantis Bug Tracker is a free and open source, web-based bug tracking system.
Redmine - Flexible project management web application
SourceForge - The Complete Open-Source and Business Software Platform.
osTicket - osTicket is a widely-used open source support ticket system.
openDesktop.org - The website openDesktop.