Odeo aims to become the premier destination for podcasting services. They have a large user base and lots of podcasts are networked through their site. At this writing I don't understand how they could have done what they have. Hopefully the quality of their service will improve in the future.
Individuals "join" the site so they can customize what they get. Anybody can add a podcast feed to Odeo, so long as they're registered.
They use a Flash player embedded on the web page to let users directly listen to content. They also offer player code that can be embedded on other sites much like the YouTube player.
They copy content to odeo's web site.
Each podcast has its own page.. they call it a "Channel". They list on that page the recent (?All?) items on that podcast.
Very skimpy topic list for browsing... go to a topic, and you've got a list of presumably the most popular items on that topic, but you can't go beyond the few items listed on that page. It doesn't have subtopics. Hence, browsing isn't a very useful activity.
They use Google Search for searching. But it's implemented rather badly.