If you can get the url of the stream you can listen. A lot of time internet radio steam are built in to the flash players so it is hard to get the url for the stream. But there ae some apps out there that will help you locate them. Just google for them.
Once you have the stream just paste it in to 'internet radio favorites' on mycast.orb.com. Then visit your mycast page on your iPhone and orb will convert the stream so it will stream to you.
I have tons of them.
This will not work for clear channel streams, they are some type of one time use token so the links can not be transported.