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