I just installed iTunes on my laptop to see if I can access our home music library over the network. (I'll blog more on that once I try it out). The installation also defaults to putting a QuickTime "Q" in the system tray. Apple doesn't make it very easy to find where you stop this "Q" from showing up, so I thought I'd share it with y'all.
Right-click on the "Q" in your system tray and select QuickTime Preferences from the context menu. Click on the Advanced tab and uncheck the Install QuickTime icon in system tray option near the bottom. Click OK and the "Q" should finally go away!