Windows only: TrayEverything is a lightweight portable application that minimises windows to the system tray even when the program lacks native support for being parked in the tray. In addition to simply minimising windows to the tray, TrayEverything also has options to add a button to the title bar of windows for minimising to the tray, hot keys to minimise, and even using inactivity as a trigger to send a window to the tray. If you'd like to keep a program running but don't need to tend to it or would like to make sure nobody messes with it, TrayEverything can minimise it without a visible icon in the tray and even password-protect it. For more system tray goodness, check out Trayconizer a program that starts your program in the system tray from the moment it's run. TrayEverything is a free download for Windows only.