My favorite math class was probably 18.310, intro to applied math, which is on ocw: http://ocw.mit.edu/courses/mathematics/18-310c-principles-of...
It's not comprehensive by any means, and you probably need to know at least calculus to be ready for most of this, but it covers some pretty cool stuff, including RSA.
MIT 18.06, 18.085, 18.086, 6.262, 6.450
Stanford EE263, EE364A, EE261
Profs Strang, Boyd and Gallager are quite a bit better with maths than the typical engineering lecturer, even though their courses are not exactly at the level of Rudin, Breiman et al.