I really like Tabula Digita's immersive 3D games for math, especially DimensionM for algebra. I recently learned that this company was the focus of an article in Forbes magazine. You can read the article online:

The Long Road to Edutainment: An entrepreneur's arduous journey to build educational games company Tabula Digita. Sramana Mitra, Forbes 8/14/09


I first came across the people behind Tabula Digita at the 2005 Serious Games Summit, and I was impressed. Students really learn a great deal about math by playing these games, and it is more exciting than completing worksheets.

Here is a link to a TV news clip about middle school students in North Carolina who are participating in a research study under the direction of Dr. Albert Ritzhoupt, of UNCW's instructional technology program:

http://www.dimensionm.com/video/wect.html

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Dimension M, a 3D Multi-Player Algebra Game