It is pretty difficult to find advanced math lectures online, though, with some effort, one can find a few (by "advanced" I mean anything beyond 1st or 2nd year of college, and preferably aimed at mathematicians, rather than engineers or scientists). The difficulty of this search becomes orders of magnitude greater if one is looking for audio-only lectures (that can be easily readily played in an mp3 player). Of course, much of this has to do with the fact that it is difficult to communicate math without visuals, although it is definitely possible.
Does anyone know of any such resources (preferably free) online?
PS: one could, with considerable additional effort, extract the audio from, say, math video lectures on YouTube or iTunes, but I'm not too keen on this option, and not only because of the work involved.