Pandora
Used by 19 peoplepandora.com ↗

“I usually don't write with music, but occasionally I'll listen to a Pandora station of whichever top 40 song my daughter is listening to at the moment.”
Joshua Davis Interview, Writer, filmmaker, co-founder (Epic Magazine) · via Uses This 
“On the home PC: Pandora is always going, I work best with music or some noise in the background.”
Chris Darden Interview, Board game designer (Dungeon Roll) · via Uses This 
“I listen to Pandora while I code.”
Bret Taylor Interview, CTO (Facebook), co-founder (FriendFeed) · via Uses This 
“Pandora for most of my music listening, and a variety of random Internet radio stations for the rest.”
Mark Pilgrim Interview, Developer & standards advocate (Google) · via Uses This 
“Though these days I'm using Pandora more and more.”
Cal Henderson Interview, Web developer, professional asshat · via Uses This