BIG Red Button is a system utility that lets you access an app quickly. One of the annoyances of both Mac OS X and Windows is that it is often hard to find one application when you are running lots of them. The Mac has let me have more open apps than ever before without slowing down my system, so this problem has become even a bigger annoyance. BIG Red Button places a button in the left-bottom corner of the screen. You can configure the application to launch an application or even an AppleScript. There is a feature called Action Slots, which lets you add more than one application. You can add the ones that you want from the Configure Action Slots screen, which you can access from either the menubar or from the information button next to the big, red button. To launch one of the applications in your Action Slots, you simply can hold the "Alt" key when you click on the button. This will bring up the Action Slots window where you can select the app or script that you want to run. You can add up to five applications to this list.
In my testing, I was able to easily and quickly add applications to BIG Red Button. The area where the button becomes active is quite responsive to mouse input. I added Mail.app as my main application so I could go back to it when I have a mess of windows opened. When I clicked on the button, Mail was brought to the front really quickly.