Under Music you can see the limited number of official options for music. I think there is an internet radio (My Streams) section that you need to put the URL stream address in and there is unlimited number of listings you can have. It has to be done manually but it is very effective. I think I have around 20-25 stations added. There are listings of urls that you can use on this forum. They work for any Chumby or chumbyized unit. I'll try to find the link to the old posts on adding stations and update this post.
Update: Check out: https://forum.chumby.com/viewtopic.php?id=9053