Everything I learned about elliptic curves, I learned from Jeremy Kun

Seriously, pretty good write up at http://jeremykun.com/2014/02/08/introducing-elliptic-curves.

It starts simple ('I aced my middle school algebra class'-simple btw) and before you know it, Abelian groups will hit you hard. Well worth the few weeks you will spend on it :)

                                                       (Credit: Math ∩ Programming)