http://www.redmine.org/
Multiple projects supportFlexible role based access controlFlexible issue tracking systemGantt chart and calendarNews, documents & files managementFeeds & email notificationsPer project wikiPer project forumsTime trackingCustom fields for issues, time-entries, projects and usersSCM integration (SVN, CVS, Git, Mercurial, Bazaar and Darcs)Issue creation via emailMultiple LDAP authentication supportUser self-registration supportMultilanguage supportMultiple databases support