Having too many windows open can seriously impede multitasking. Trying to find the right window, whether through the taskbar or through Alt-Tabbing , becomes an awkward juggling act. Minime (free) lets you easily hide windows which you don't want cluttering up your screen.
Using a customizable hotkey, Minime minimizes programs to the system tray. There's also a handy hotkey for restoring everything you've hidden. Minime groups all minimized programs together in one tray icon, unlike RBTray, which creates a separate icon for each. Right clicking the icon brings up a list of the minimized programs (along with a link to Minime's settings), each of which can be selected for easy restoration. This is very nice improvement, because a cluttered tray can cause headaches too. And whereas RBTray doesn't work on some non-standard windows, such as iTunes, Minime handled everything I threw at it.
Having programs grouped in the tray may seem odd at first, but it's not hard to get used to it. And once you do, you'll probably realize that there are a lot of programs that never belonged in your way in the first place. Minime is a small utility, but can still dramatically improve your productivity.