Anyone have any leads on a wifi remote control application for common music players (e.g. iTunes, Winamp, etc.)? The iPhone has a great application for this, but I have never found a good one for BB.

Well, of course the iPhone works with iTunes, they're both made by Apple and they made a specific effort to integrate the two products well with each other.

I highly doubt one exists for the BB. It would require a plug-in to install on your PC with your media player, and going over wi-fi... I would guess the demand is simply too small for a developer to muster the effort to start on something difficult like this.