iAdjust Audio 1.0

iAdjust Audio 1.0 offers you a free program allowing you to adjust the main volume in smaller increments than the standard 16 moves via the keyboard. Because of variations in operating systems, these scripts will give you between 44 and 48 increments.

Leopard and Snow Leopard users can hold down the Option and Shift keys while pressing either volume key to get very small increments (64). I find this awkward as it requires both hands.
Of course, if you're satisfied with using the keyboard or moving a slider, there is no reason for you to download these two scripts.

Requirements: PPC/Intel, Mac OS X 10.4 or later