Daniel Haverman has released ShoutPSP, heres whats in the readme:
ShoutPSP is a piece of software the will connect to a shoutcast server and fake it's a file download instead of a stream. This means your PSP will think it's a normal file-download (of 1GB large). If you put such a file in an rss feed it allows you to listen to your favorite shoutcast servers on your PSP anywhere and even with firmware 2.7
Parameters:
ip - the ip-address of the Shoutcast server
port - the portnumber for the Shoutcast stream
stream - the file-location of the stream