GanttProject is a cross-platform desktop tool for project scheduling and management. It runs on Windows, Linux and MacOSX, it is free and its code is opensource.
Gephi is an interactive visualization and exploration platform for all kinds of networks and complex systems, dynamic and hierarchical graphs. Runs on Windows, Linux and Mac OS X. Gephi is open-source and free.
This is a suite of macros to perform basic statistical analysis within OpenOffice. These macros give OpenOffice Calc the functionality which Analysis ToolPak gives Microsoft Excel, and many of these routines are unavailable in Excel.