Nomad PIM is a free extensible personal information manager. It contains modules for personal notes, journal, address book, personal finances, task management, time tracking and evaluating basic fitness measurements.
GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching geometry, algebra, statistics, and calculus. Download the free software at http://www.geogebra.org. Find the source code at http://www.geogebra.org/trac