The mainstream market for podcasts is still yer typical horny geek. Look at whats on the top ten - maybe shows like Keith & The Girl are like Stern, and yer typical geek is into technology and scifi. The only easy way to get podcasts is via iTunes, and while there are lots and lots of iTunes subscribers, its still not the biggest part of the population. Podcasting needs to be as easy as: they start playing when you start your car, just like radio. How do we solve this problem? Heres my 2 point plan (can you tell I love 2 point plans?)
1: Since radio is dying, have the biggest podcasting publishers (like podshow) go out and buy some of these radio stations. They don't have to be big stations, just little stations in major markets, and play podcast after podcast. You may have to time delay and bleep out stuff in order to get past the FCC, but it will give the rest of the population access to the podcast. And like in commercial radio, you can run ads in between, make some money, and share it with the podcasters.
2: Right now, iTunes will give you a list of similar podcasts, based on what other people have subscribed to. But this is just connecting podcasts to podcast (tail content to tail content), we NEED some way in which to connect head content (like big radio and TV celebrities) to tail content (podcasts). For example, if you like Howard Stern, you probably like Keith & The Girl, if you like Rush Limbaugh, you probably like THINKfuture Radio, if you like NPR, you probably like Blast The Right. If you read the Chris Anderson whole head-tail content thingy, simply having the tail content available on the net is not enough - you NEED to connect the head content to the tail content in some way. In this way, you can guide folks to podcasts they may like based on the "head" content that they like. Only then can you start drawing people away from the head to the tail. And all of us "tail" folks like that thought.
So ya, its not simple, or cheap, but nothing ever is is it? Although, i don't see how a few programmers in a room cant throw together my point 2. As a matter of fact, one of the big directories should do just that. Are you listening Alley or Pickle or Pluggd?