Project management software, online collaboration: Basecamp. Highly recommended.
Primarily through word-of-mouth alone, Basecamp has become the world’s #1 project management tool. For the last 10 years, companies have been switching to Basecamp because it’s famously easy-to-use, reliable, and It Just Works™. The Trac Project. Redmine - Overview. Bugzilla.org. Pivotal Tracker: The iPod of project management software.
Bug, Issue and Project Tracking for Software Development - JIRA.