In addition to all the wonderful resources already suggested above, you should check out the MOOCs on Mathematical Thinking (https://class.coursera.org/maththin

In addition to all the wonderful resources already suggested above, you should check out the MOOCs on Mathematical Thinking (https://class.coursera.org/maththink-2012-001/class/index https://class.coursera.org/maththink-2012-001/class/index) and Algorithms (https://class.coursera.org/algs4partI-2012-001/class/index https://class.coursera.org/algs4partI-2012-001/class/index) on Coursera.