iTunes Remote for Windows Phone 7 controls playlists, volume, and multiple libraries
The mobile app gives you complete control over iTunes playback once you've paired it with your computer using the free desktop pairing software. In addition to showing you what's currently playing, iTunes Remote also lets you browse and search your collection. All the playback controls you'd expect are offered -- you can pause, resume, skip, stop, and adjust the volume. iTunes Remote also supports multiple libraries, so you can control playback from as many iTunes instances as you please.
iTunes Remote for Windows Phone 7 sells for $1.99 in the Zune Marketplace.
Download iTunes Remote for Windows Phone 7 [Zune link]