Now there is an open source tool for project scheduling called Open Workbench. According to OpenWorkbench.org, the tool provides functionality in "project planning, project scheduling, resource management, project review and more." It might be viewed as the open source alternative to Microsoft Project.
It's intended to be a MS Project replacement but our testers found it hard to use.
But it's worth taking a look at - after all you can't beat the price.
Curt Finch is the author of a project management book and lives in Texas.