Weka, a data mining software.
Pentaho open source (business) data analysis. It is possible to extend it with R analytics.
Orange, Open source data visualization and analysis for novice and experts. Novices can get going through visual programming.
Somewhat relevant too, a page on Information Visualisation, techniques and resources on WikiEducator. The primary goal is to encourage the teaching or use of information visualization at school here in NZ, but many links reflect industry / real-life usage.