I'm kinda the guy real jazz buffs hate. I like smooth jazz, and I'm not really looking for music that "challenges" me. I just want music I enjoy. But Jazz24.org out of Washington state plays a little bit of everything jazz, including many classics with very little repetition like you'll find on Pandora, which I also enjoy.
And, right now, Jazz 24 has unveiled the 100 greatest jazz songs as voted on by their listeners. Even better, they now have a constant stream of the 100 greatest jazz songs. When you need some great jazz in a pinch, it's a handy link.
I was listening to it at work today because most jazz does not have vocals to distract me. It also helps me chill out in a high-stress, always-on-deadline environment. And people have learned over the years at work that if CJ is wearing his headphones, your question better be important.
Ah, the many benefits of jazz.