You could use this :
http://jeanmatthieu.free.fr/cocoajt/ . In the menu called 'Magneto', click on "Enregistrer un flux..." (="Record a stream") and just paste the link of your real audio stream. If you only got a RealAudio File, just drop it on text edit's icon and it will give you the link you should paste in CocoaJT.
The program is in french, but it is the only one I know which will record the stream as a real audio file. So you can't listen to it in iTunes, but you get a much smaller and better sounding file than recording it in aiff and then re-encoding it in a small mp3.
Oh, and it's free.
(you-hou, first post!!)