This is Jeff Erickson's free textbook (really a set of detailed lecture notes) on Algorithms, a course that Jeff teaches at UIUC and routinely wins teaching awards for. Definitely worth your time. Jeff is working on a similar set of notes for Computational Topology: http://www.cs.uiuc.edu/~jeffe/teaching/comptop/schedule.html. These are not as developed yet. He's also written an interesting piece about getting into a graduate school with low grades: http://3dpancakes.typepad.com/ernie/2005/03/re_phd_with_low.....