http://www.math.hmc.edu/calculus/tutorials/vectoranalysis/

 

Gives a review of the basic ideas of standard 3 dimensional vector analysis.

 

http://en.wikipedia.org/wiki/Geometric_algebra#Three_dimensional_vector_relationships_vs_N_dimensional_equivalents

 

Gives a good review of the basic ideas of and history of geometric algebra.

 

http://modelingnts.la.asu.edu/html/intro.html

 

This is David Hestenes’ website, with many applications of geometric algebra to physics.