I used to use a Logitech G11 keyboard which had a useful Mute and Volume +/- buttons on it but I recently switched to a Das Keyboard which I love, but has no gimmicky buttons.
Since I like being able to control the volume without having to open the Volume Panel, I looked for a software solution. I decided to opt of AutoHotKey and create a very small script that does the job nicely:
#WheelDown::Volume_Down #WheelUp::Volume_Up #MButton::Volume_Mute
I can now control the volume Up / Down by pressing the Windows key (#) and toggle the mute by clicking the middle button (MButton).
You can get the script here.