WebSynthUI
WebSynthUI is a collection of HTML5 UI components that I designed for a Web Audio project I'm working on, but that could be just as useful in other interfaces. It currently consists of a rotary knob, a segmented switch and a toggle switch.
I plan to add more components as I have time. The most obvious omissions from the current collection are horizontal and vertical faders, and a momentary switch or trigger pad, so I'll try to get to those soon.