There are two free Udacity courses I can recommend: https://www.udacity.com/course/computability-complexity-algo... and https://www.udacity.com/course/intro-to-theoretical-computer... And Tim Roughgarden's lecture series: http://timroughgarden.org/videos.html The material isn't advanced though. For advanced comp sci courses, you probably have to pay for them. At least I haven't found anything free available.