"If you've been looking for a way to easily control your PC's music collection with your new Windows Phone 7 handset, have a look at the Remotive app created by Sharkfist Software. The $1.99 app allows you to remotely navigate your music collection on your Windows Media Center PC (requires the installation of Remotive Server for Windows Vista/7). With this app, users can browse by album/artist/album artist, select music, and see what's currently playing. A future update will bring remote volume control."
Remotive looks to be an awesome and easy-to-use Windows Media Center remote application for your Windows Phone 7 device. With it, you can control your music anywhere in the house--or even all over the world--from your home machine to your handset. It's attractive and fits with the Windows Phone 7 / Zune aesthetic, and it all seems to be fairly snappy. A server application (free from the developer's website) installs to your Windows Vista or 7 PC and handles all of the setup for you, with a few extra tweaks needed if you want to use Remotive over your cellular data network. Albums display with thumbnails and can be grouped by artist, and just as in the Music app a long press will give you options to play or add to quick list. Volume control and search features are coming in a future release. For more info, James from the Digital Media Zone gives a good walkthrough in this YouTube video. The app is $1.99, but a free trial which limits control to the first 50 albums/artists will give you a sense of what the app can do.