The standard reference (in the "That's what MIT uses" sense) is Introduction to Algorithms[1], as you probably know. It is a wonderful book and I have a copy that is wearing of because I use it so much.

As for "outside of a classroom setting", the best book I can recommend is "The Algorithm Design Manual" [2]. It is worth its weight in gold. Very user friendly, as I never though an algorithms book could be. It contains dense material, but at the same time reading it feels like reading a good fiction book. I first heard of it while reading Steve Yegge's post "get that job at google"[3], bought a copy and, wow, what an amazing book.

[1] http://mitpress.mit.edu/algorithms/ [2] http://www.algorist.com/ [3] http://steve-yegge.blogspot.com/2008/03/get-that-job-at-goog...