I use this NPTEL site for online lectures they give us more information on a specified topic and goes more in depth than our faculty teaching us . I also used these lectures for my competitive exams and not all of them are good you have to select the good lecture who is best for that toic or subject, one can easily find the well known one in no time. It updates its vedios on new topics but mostly some of them are very hard to understand because of their standards are high. It would be really helpful for students who is willing to gain more information . They can also be found on youtube so there is no wate of time for loading it.