It has been around for a while and they expanded their stations over time. I listen to the Sondheim station a lot. For general listening I prefer BWW's station but for specific listening, I love AccuRadio. I also like that you can listen to music from certain time periods. They don't take requests though.
I certainly agree with all the more obvious choices already listed. However, one of my personal favorites (if we're including entr'actes) is the entr'acte from The Scarlet Pimpernel. Say what you want about especially the later versions of the show (and I'll agree with you), but I just LOVE the entr'acte, especially the trombone counterpoint at the end.
frontrowcentre, I'm with you on Bells Are Ringing—I adore that overture! (I'm so glad the show is getting another shot at Encores after that blasted revival ten years ago. Do it right this time!) Just listened today to the overture of the 1971 revival of No, No, Nanette after many, many years. Wow. It's wonderful! Give it a listen if you haven't lately.
I saw Idina Menzel at the Cincinnati Music Hall on Sunday. Before she performed, the Cincinnati Pops played several selections from Broadway musicals. I was very excited when they played the West Side Story overture. It was fantastic.