Here I go monopolizing the Resources page again!

NPR will be streaming some portions of the Newport Jazz Festival.

Full article: http://www.usatoday.com/life/music/news/2008-07-30-newport-npr_N.htm

So you don't have to sift through a lengthy article:

"On Saturday and Sunday, NPR plans to webcast performances by Jim James of My Morning Jacket, Jakob Dylan, Richie Havens, the Cowboy Junkies, Steve Earle, Brandi Carlile and others. The concerts also will be broadcast live on member station WFUV-FM in New York City.
...
Select acts from the jazz festival also will be webcast, as well as be broadcast live on WBGO-FM in Newark, N.J."

(Just to make it easier, that's www.wbgo.org and www.wfuv.org-- the former has an all jazz format.)

You can find your local NRP station at www.npr.org. (wow that sounded like a commercial)