Looking for a way to stream your iTunes library over WIFI or 3G? I just picked up StreamToMe. It works great. It automatically picks up your local (wifi) iTunes libraries, but you manually re-add your library in order to get it to work over 3G.
The app is $2.99 and works on iPhone, iPod Touch, and iPad. If you download the app, you will also need the free server software found here.