Tick tack... tick tack...

I will have to think about debouncing a bit, but in general it works quite nicely. In this picture it controls the lights used to illuminate it. The lights understand serial, so the knob only has to send '+' or '-' to adjust brightness.

It also works very nicely as a volume knob for amarok, kmix ... only requires linux, KDE4 ;-)

The ATtiny85 is hidden on the other side ;-)

As usual you can have all design files and code. Search for "Serial-Knob" and take a look inside the "ATtiny_projects" repo for code: [1],[2].