In the flavor of "Wouldn't it be nice if there's somewhere where I could look up X," I think the database could probably use a list of online lectures which are freely available, e.g. some entries given by this MO question.
In the same vein, I could also imagine listing lecture notes people have prepared for courses, but this would be harder since there are so many places online where professors have posted their lecture notes and it can be difficult to say when one set of lecture notes is "better" than another. Still, having online lectures as well as resources for teaching (e.g. calculus applets) would fit the bill of things I like to look up but often have to search all over the web for.