GanttProject is another project management software program that came to my attention via a posting on yesterday's OpenProj software. I'm not sure which is best, GanttProject has more screen snapshots and more listed features than does OpenProj. They both look great and they both work on all the major operating systems.
They both look like they are worth a shot. I don't use this type of software; please leave a comment if you have used one or both of these programs.