I've looked around, but I haven't seen anything promising. Is there an iTunes radio station client that will run on my SL-5600? I could only find tckRadio (which is $15 and hasn't seen an update in 3 years) and Handango ZRadio ($10 and nearly as outdated). I'm really looking for something iTunes station compatible, but would settle for any robust app. Thanks.

There is a nice application for playing shoutcast radios, with integrated search for stations from shoutcast.com. I think it is very good app.
http://hake.syuriken.jp/shoutcast/index.html

Don't know if it is iTunes radio station compatibile (I suspect it is) but you may want to give Zplayer a try. It relies on mplayer (running in the background), but plays mp3s, oggs, and streaming audio (I am playing a shoutcast stream right now). You can find it at:
http://atty.skr.jp/zplayer/

I hope this helps,

Craig...

EDIT: My mistake, zplayer runs on the Sharp ROM, not sure if it runs on OS.