The USB Overdrive is a universal USB driver that handles all USB mice, trackballs, joysticks and gamepads from any manufacturer and lets you configure them either globally or on an application-specific basis. It reads all kinds of wheels, buttons, switches and controls and supports scrolling, keyboard emulation, launching and complex macros as well as all the usual stuff like clicking, control-clicking and so forth. The USB Overdrive can easily handle several USB devices at once- I have two mice, one trackball, two joysticks and one gamepad connected to the same iMac, and each of them comes from a different manufacturer.
Because each control in each device can be fully configured, the USB Overdrive lets you use any joystick or gamepad with any game, including the ones that don't support Apple's InputSprockets. You can map your joystick movements and buttons to the keyboard and mouse to make the game believe you're playing on the keyboard, and you can do this mapping separately for each game so that it's immediately available as soon as the game is launched.
For games that already use InputSprockets, the USB Overdrive provides all the needed hooks to support the device-specific configuration panels provided by the manufacturer.
The mouse settings allow you to speed up your daily tasks by assigning useful actions to all the extra buttons and wheels in your USB mouse. You'll typically want to assign a control-click to the right button for easy contextual menu access, and enable document scrolling if your mouse has a scrolling wheel.
The Control Panel includes an active help feature that explains each command and option as you move the cursor around.