Some good ones from Stephen Boyd - helped me really grok the subjects. Signals and Systems: https://www.youtube.com/watch?v=9gPuUVYImiQ&list=PLpGHT1n4-m... Linear Dynamical Systems: https://www.youtube.com/watch?v=bf1264iFr-w&list=PL06960BA52...

This series on Finance Theory by Andrew Lo unfolded just during the 2007-08 crisis - so that's an added bonus as the lectures refer to ongoing events sometimes. https://www.youtube.com/watch?v=HdHlfiOAJyE&list=PLUl4u3cNGP...