For further information...

http://modelingnts.la.asu.edu/ (Hestenes Group)
http://www.mrao.cam.ac.uk/~clifford/ (Cambridge Group)
Matlab Tutorial (soon)
- http://carol.wins.uva.nl/~leo/clifford/ (Leo Dorst)
  with links to other Geometric Algebra material
- http://www.cgl.uwaterloo.ca/~smann/ (Stephen Mann)