ProjectForge aims to be an extensible online project collaboration suite with heavy emphasis on software project managment and integration with a variety of scm's.
SEE -- www.projectforge.org Very good. A bit tricky to install but with a tomcat knowledge you should be OK. Once installed it gives quick response, pleasing layout, full project hierarchy, very configurable, does Gantt charts, timesheets, calendars, the data entry is smooth and not too tedious. It knows about holidays and weekends. Also supports Asterisk integration for phone book and "click to call". This is the most attractive open source web-based collaborative project system I have seen so far.