The iTunes App Store is filled with applications that let you control desktop media players from your phone. There are remotes for iTunes, Boxee, VLC, and other apps. And then there’s RemoteX — a single application that functions as a remote for all of those apps, plus 9 more.
RemoteX is compatible with Windows XP, Vista, or Windows 7, and requires you to download a small server utility on your PC. Then you fire up the RemoteX app on your iPhone or iPod touch, connect to your desktop (which should automatically show up in the list of servers), and choose the media player you want to handle. The remote control functions change for each app. For instance, the VLC controller has FullScreen and DVD butons, while the Winamp controller has an Equalizer and Playlist button.