I am very excited about this site. I found out about it through the Kidcast podcast I subscribe to. Innertoob allows you to create markers within your podcast, but the great thing about it is that the content you add to these markers is accessible by search engines. I will be posting some more about it as soon as I get to try it out.
The same people responsible for Innertoob have also created Crowdabout. This is a flash application that allows people to insert audio/text/video comments into your existing podcast and turn it into a conversation and make it more interactive. Again, I just found out about these two sites so I have not had a chance to give them a full trial yet.