I haven't seen this talked about on here. Justin Angel has created a .xap that streams pandora and acutally works very well. The only thing it doesn't do is run in the background and show the now playing media on the lockscreen. If he could get that working, it would be amazing.
http://twitter.com/#!/JustinAngel/status/123225742199881729
http://twitter.com/#!/JustinAngel/status/123225742199881729