Watchcat is a little program I've had for a long time that's extremely useful. It allows you to hide programs in the background without having them clog up the taskbar.

I have a few programs that I always have running: iTunes, Mozilla Thunderbird (email), Feedreader...and it is annoying having them always in the taskbar taking up space. This little tool allows you to hide programs by clicking on its icon and selecting which to hide. you can also set hotkeys to hide all open programs, unhide all, hide desktop, turn on screensaver, and many other things.

Download it, install it, and try it out. You'll definately find it useful.