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
The LabView of NI is a very attriactive tool and affords enough money but leaves no competitor. Although, there are some good HW manufacturers but is limited because of software. So if there is a good SW free, they can make cheap and good product.