I'm a big fan of apps that integrate desktop usage with a supplementary (but solid) mobile app. ex.fm is now among those that can claim to be such. You can use their desktop browser service to queue music, catalog it, love it, etc and then launch their brand new iPhone app to access it on the go. I'm not entirely convinced on any mobile music app quite yet because I don't think the providers have stepped up their bandwidth game to make true streaming a reality but it certainly looks like exFM is giving them good reason to push things forward.