artlinks: sound and Radio 
RE-Inventing Radio: part II
I guess this is sort of out dated, but anyway...

wps1 Art Radio

german from austria

great project by 2005 exiting de appel curator students in amsterdam

New American Radio
not the most interesting site on the net, but it is an archive and there are some interesting pieces there.

Brainwashed Radio!!

Art Radio Seattle
a bit boring, but...

National Gallery of Art - Radio Programs
more art history, but I like this piece on Ginevra ...

Again: more sound than radio, but still...

New Adventures in Sound Art
more sound art and less art radio, but very good.

Radio Art Companion. A finished project, but good...

Resonance 104.4 fm clames to be Londons first art radio. the only eastern european art radio/sound art site I found

negativeland's Over The Edge (OTE)
every thursday at 12pm -east coste time in USA
started 17.november 2005!!

Deep Wireless 2005
they call themself "A Celebration of Radio Art"...