Steven Wittens has created a ridiculously cool DHTML HSV colourpicker, which cunningly uses overlaid transparent PNGs to get the SV square in the middle. Not content with that, he also created a way to turn a select box into a discrete-mark slider bar using only CSS. See his full blogpost for more details.
Seems to be stuck on one color: burnt server.
It is pretty cool, but it is not an HSV color picker. It is an RGB color picker. HSV is a different colorspace, not just a style/type of color picker. HSV isn’t even mentioned anywhere that I see.
This is technically impressive but I think the UI would be simpler with one colour rather than 4.
HeroreV: it is HSV. The hue is the outside circle, vertical movement is the value (brightness) and horizontal movement is saturation (moving from pure colour to grey). If you check the Wikipedia article on HSV, you’ll see a diagram much like the widget.
Jan: Oops, you are right. Sorry.