We've seen little DIY volume knobs before, and they're a handy way to add means to finely adjust the volume on your computer. Instructables user Trochilidesign's made their own, and it's pretty futuristic looking.
Aside from the components of the knob itself, Trochilidesign packs in an LED ring so the knob can glow a variety of colours. Otherwise, the knob is encased in a wooden cover and powered by a Trinket that turns the input from the knob into keyboard commands. It's a fun project and one that you can easily adjust to suit your needs. Head over to Instructables for the full guide.
USB Volume Knob [Instructables]