My colleague Richard Rand is one of the world’s experts on nonlinear vibrations. He’s posted his lecture notes (free!) that include topics you won’t find anywhere else, like delay equations and fractional derivatives treated with perturbation methods. ecommons.cornell.edu/bitstre…

“Fluid Mechanics Lectures for Scientists and Engineers”. This is a fantastic collection of films, made about 60 years ago, by the world’s greatest experts in fluid dynamics at that time. The one by G.I. Taylor, on low Reynolds number flow, is extraordinary cosmolearning.org/courses/fl…