Geometric Algebra - David Hestenes
http://modelingnts.la.asu.edu/
University of Cambridge - Cavendish Laboratory group
http://www.mrao.cam.ac.uk/~clifford/
Clifford Research Group - Ghent University
http://cage.rug.ac.be/~fb/crg/
Rafal Ablamowicz
http://www.math.tntech.edu/rafal/
Leo Dorst
http://carol.wins.uva.nl/~leo/
William Baylis
http://www.cs.uwindsor.ca/users/b/baylis/index.htm
Bertfried Fauser: Links
http://clifford.physik.uni-konstanz.de/~fauser/P_cl_people.shtmlInternational
Clifford Algebra Society
http://www.clifford.org/
Google Geometric Algebra Web Directory
http://directory.google.com/Top/Science/Math/Algebra/Geometric_Algebra/
Clifford Algebra to Geometric Calculus - book by D. Hestenes and G. sobczyk
http://www.amazon.com
On the Evolution of Geometric Algebra and Geometric Calculus
http://modelingnts.la.asu.edu/html/evolution.html
Geometric Algebra - Japan
http://sinai.mech.fukui-u.ac.jp/gcj/gc_int.html