I've listened to podcasts and visited YouTube before so I know my way around them already. The majority of podcasts I have downloaded to my iPod have been film-related and I mainly use YouTube to look at new movie trailers, so it was good to look at them both from a professional point of view to see how they could be of benefit to libraries.
The library podcasts that I listened to and viewed all seemed very useful and informative. I wouldn't use podcasting myself, as I'm more of a writer than a talker, so personally I'd be more comfortable using things like Twitter and Facebook. However, for those who have the gift of the gab, I'd imagine it could be a new and fun way to market your services to readers.
I'll leave you with Monty Python's 'Gorilla Librarian' sketch, which I found on YouTube: