If you haven't used it already, Versor[0] is nice to play with. GA is simple enough that even normal-ish teenagers can understand it and produce useful results (my sons are using it in a game they're building). Math isn't even close to my strong suit, but Dual numbers and GA make sense to me, and have made it a lot easier for me to do (seemingly, to me anyway) advanced stuff. :-)

[0] http://versor.mat.ucsb.edu/