Another free alternative, as long as you can look up the stream URL, is the 'Web Radio' Safari extension. Elegant, hides away when you don't want it, works great:
http://safariextensions.midwinter-dg.com
(HINT: Find stations you like in iTunes; Start them playing; Right-Click on the player sub-window at the top and 'Get Info'; At the bottom of the 'Summary' tab will be the stream URL; Copy it using another Right-Click and 'Copy URL'; Paste it into Web Radio and name the station).