I like to listen to the "Ambient" radio in Grooveshark. For this, I don't need to load the whole site. A nice and lightweight way of doing it is to use the new HTML5 interface of Grooveshark (originally design for mobile devices and currently in beta): http://html5.grooveshark.com.
You can't log in and load a playlist or whole record, but for radio stations is great!
