What are some alternatives?
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.
GitHub - Originally founded as a project to simplify sharing code, GitHub has grown into an application used by over a million people to store over two million code repositories, making GitHub the largest code host in the world.
Pivotal Tracker - Pivotal Tracker: The awesome, lightweight, agile project management tool for software teams. Get your 30-day Free Trial started today!
GitLab - Create, review and deploy code together with GitLab open source git repo management software | GitLab
Redmine - Flexible project management web application
FogBugz - FogBugz is the world's easiest bug tracking system, built for teams who are serious about shipping great software.