GanttProject is a free, open source project management software. It is mature and probably one of the most complex project management tools which offer an impressive list of features considering it's a free program distributed under the GNU General Public License.

Features:
- create Gantt charts
- create and organize tasks in a "Work Breakdown Structure."
- develop tasks and milestones.
- you can draw dependency constraints
- create baselines
- generate PERT chart from Gantt charts
- create and assign human resources
- monitor task assignments
- use collaboration (WebDAV and cloud storage)
- create reports (in PDF, as a PNG/JPEG image)
- export to CSV and Microsoft Project
- import from Microsoft Project and iCalendar format

Whats New:
Updates: official site does not provide any info about changes in this version.