Is there any way in Lion to have "Natural" scrolling for trackpad and "reverse" for mouse? [duplicate]
You may try Scroll Reverser. That screenshot says it all; you can invert scrolling per-axis and per-device, individually for trackpad and mouse.
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Use USB Overdrive -
With USB Overdrive, it is possible to alter any button on any input device like your mouse, and you can define specifics for a particular mouse or input device to suit your need.
All you need to do is to alter wheel up and wheel down for your mouse to be the opposite direction, so that wheel up is down and wheel down is up, and you can still retain the regular behavior for other devices.