I'm looking for a single word that describes both webinars and podcasts. Any ideas?
I would suggest the word broadcast. A few decades ago, it was used as a hypernym for radio and television shows, and many dictionaries still explicitly list those media in their definition of broacast. However, in today's world – where people make phone calls over the internet – media boundaries are becoming more blurred than ever; I don't think anyone would have trouble expanding the boundaries of broadcast beyond radio and television. You could even specify internet broadcast if you felt like broadcast alone was not suited for your purposes. Webcast might be yet another alternative.
A webinar would be a two-way internet broadcast medium, while a podcast would a one-way internet broadcast medium.
Interestingly enough, the word broadcast was borrowed from agriculture, so it wouldn't hurt to bend it a little bit more than it's already been bent.