My videos in english language:
I have just began to produce videos in english language (I started 29.April 2012)

  
Differential calculus

Learn differential calculus in 10 minutes:
http://www.youtube.com/watch?v=_ON9fuVR9oA
  
  
Vectors:
Angle between two vectors:
http://www.youtube.com/watch?v=YYQo2uUCvo4