The Integrated Land and Water Information System (ILWIS) is a PC-based GIS & Remote Sensing software, developed by ITC up to release 3.3 in 2005. ILWIS comprises a complete package of image processing, spatial analysis and digital mapping.
SharpMap is a simple-to-use map renderer that renders GIS data for use in web and desktop applications. The engine is written in C# and based on the .NET 2.0 framework.
SAMT - Spatial Analysis and Modelling Tool - A modeling system with a few GIS-features, like spatial analysis, some spatial techniques and a simple in and export function to a GIS. The main focus is to have an open system to include different models.
HidroSIG - A Geographical Information System (GIS) with special tools that will allow you to make estimations and analysis of hydrological, climatic and geomorphological variables.
GeoVISTA Studio is an open software development environment designed for geospatial data. Studio is a programming-free environment that allows users to quickly build applications for geocomputation and geographic visualization.
VGMap is a new library created by Eyebeam R&D that allows designers, developers, and mapping geeks to overlay data on top of Google Maps in a richer way than is possible using their standard system. It is called VGMap because it adds vector-drawing capability to the already-awesome GMap API.
I Hope these prove useful to you. If you are new to GIS, check out the Learn2Map GIS Tutorial and Atlas. We have more free GIS software available and there is plenty of free data and shapefiles that will work with these programs. More to come!