[Basecamp] pros: works well for small groups, good communication cons: easy to outgrow, ticketing challenging
[Redmine] pros: open source, software projects, popular among code4lib responders, ties together issue tracking, documentation wiki, and source code browsing
[Trac] pros: ties together issue tracking, documentation wiki, and source code browsing
[Open Atrium] pros: drupal distro, locally hosted, customizable cons: Extending needs technical know-how, 6.x-base install, build your own drupal PM will probably meet your needs better if you have the time.