Vi Hart's wonderful take on infinity!
Dr Trefor Bazett, one of the best Maths YouTuber's for undergraduates
Grant Sanderson's beautiful summary of Pythagorean triples
Below is seminar by one my favourite lecturers of all time, Professor Anthanasios Fokas
Godel's incompleteness theorem
Dr Dan Gusfield from UC Davis, Godel's first incompleteness theorem
Dr Dan Gusfield UC Davis, Godel's second incompleteness theorem
Professor Darren Crowdy's wonderful incorporation of Complex analysis into linear fluid dynamics problems.