I forgot to mention opml manager. Some people (myself) use it as another method. I built my own directory which shows up in the podcasting app.
It's mentioned at the s60 blog as well.
http://blogs.s60.com/nokiapodcasting/2006/10/transferring_feeds_between_com.html
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TIP: You can create your own free OPML directory from www.opmlmanager.com. You can manually add your new opml file to "Directories" (Directories > Options > New > Web Directory) or save and import (Directories>Options>Import OPML File)
Once your OPML file is on your Nokia Podcasting, then you can share it with others.
