Algorithms: http://www.cs.sunysb.edu/~algorith/video-lectures/1997/lecture1.pdf
Asymptotics: http://www.cs.sunysb.edu/~algorith/video-lectures/1997/lecture2.pdf
NP-completeness: http://www.cs.sunysb.edu/~algorith/video-lectures/1997/lecture22.pdf
Table of videos and links: http://www.cs.sunysb.edu/~algorith/video-lectures/
Intro to time complexity: http://www.leda-tutorial.org/en/official/ch02s02s03.html