For Class 11 or 12, & interested in IIT preparation :
The IIT-Professor Assisted Learning (PAL) video lectures for Class XI and Class XII can be accessed on You Tube through the links shown below. Many faculty members from various IITs have contributed to these lectures.
Prof. Ravi Soni from the Dept. of Physics, IIT Delhi is the national coordinator and IIT Delhi has coordinated this entire effort with funds from MHRD.
Over 600 hours of lectures in Physics, Chemistry, Maths and Biology are available for students.
Biology : Channel 19
Chemistry : Channel 20
Mathematics : Channel 21
Physics : Channel 22
These videos can also be accessed on Doordarshan Freedish DTH. Complete list of videos is available at (Channel 19,20,21 and 22)