Calculus:
PatrickJMT – http://www.youtube.com/user/patrickJMT/featured
Khan Academy – https://www.khanacademy.org/
SOS Math – http://www.sosmath.com
Physics:
Minute Physics – http://www.youtube.com/user/minutephysics
SciShow- http://www.youtube.com/user/scishow?feature=watch
Miscellaneous:
Doodling in Math – http://www.youtube.com/user/Vihart?feature=watch