Academic Earth (www.academicearth.org) could be a student’s best source. The site offers free access to video courses and academic lectures from leading colleges and universities in one educational repository. Anyone can watch the same full-length lectures for free. New videos are added every day by college professors. Lecture videos can be browsed in four different ways: subjects, universities, instructors, or playlists (http://www.academicearth.org/about). I recommend this resource for any student struggling with algebra, physics, and so on.