I'm sure almost everyone here is familiar with Air America Radio and Nova M Radio:
http://www.airamerica.com/ and
http://www.novamradio.com/ I hope most also know of Ben Burch's Head On Radio Network
http://headonradionetwork.com/ .
Another approach, rather than the talk show format, is used by Radical Radio to help provide an alternative to the Mass(acred) Media provided by the Corporate overlords.
http://radicalradio.org/They have a weekly playlist of a couple thousand pieces (from 90 second songs or poems to 90 minute lectures from which they select 20 hours or so every few days and then run the stream with that content until the next playlist is initiated and the whole set 2000 or so gets played during the week. This week's list is on the home page.
The listen link is
http://live.str3am.com:2850/This is their self-description:
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Radical Radio is a non-commercial news, analysis and commentary-based alternative news radio that is comprised of an 18 - 25 hour program that is updated every 2-3 days and features current alternative news from sources like Democracy Now, Free Speech Radio News, the Shortwave Report and international Indy Media reports and mixes them with political speech from groups or personalities such as Howard Zinn, Michael Parenti, Noam Chomsky, Angela Davis and many, many others. This is peppered with music and poetry. We aim to offer the best in alternative news radio available on the web. We hope you like the taste more than the bland pablum of commercial radio, or the middle of the conservative perspective that NPR dishes out.. Stay tuned, stay informed and stir it up!
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Maybe others have some other lesser-known online streaming resources they can add.