For Gantt charts, there's GanttProject on sourceforge, written in Java. It does pretty well for planning most moderately complex projects. There's Omniplan by the Omni group (
The Omni Group) for $125, and, while I haven't used it, I've used other Omni group programs and they have the best-polished programs on earth (OmniGraffle and OmniOutliner are best-in-class for polish).