Algebra as geometry

I love this simple, obvious geometric proof that (x + y)^2 = x^2 + 2xy + y^2. I wish someone has shown this to me when they first taught me algebra; it would have made things a lot clearer to me.

[Image from: http://www.mathaware.org/mam/00/master/essays/B3D/2/binomial.html]

Algebraic surfaces

I like this list of mathematical formulas for describing shapes (or, in fancy terms, 'algebraic surfaces'). You can try these out with the 'Grapher' program that Apple ships with its system (or any other 3D graphing program).