JIRA

Jira is used for issue tracking and project management by over 75,000 customers in 122 countries. Some of the organizations that have used Jira at some point in time for bug-tracking and project management include Fedora Commons, Hibernate, Twitter, Skype Technologies, NASA, the United States Department of Defense and The Apache Software Foundation, which uses both Jira and Bugzilla. Jira includes tools allowing migration from competitor Bugzilla.