Learning Maths suddenly got easier when Kalid entered the scene. Better Explained has a 'A Visual, Intuitive Guide to Imaginary Numbers' that's every bit as penny-droppingly fantastic as his guide to exponential functions and e.
Trigonometry is great, but complex numbers make ugly calculations simple (like calculating cosine(a+b) ). This is just a preview; later articles will give you the full meal...
Kalid's excitement for maths is infectious and I think this is because he gives off the impression that he's only just got it himself and is desperate to share this enlightenment with the world.
Stumbled on this intuitive explanation of 'e' via a reddit comment today. Absolute internet solid gold - this is the first time I've actually understood exponential functions rather than just plugging 'e' into a formula. The rest of the better explained site looks promising too!