NOTE TO CS5 USERS: I've gotten reports that in CS5 (and maybe CS4 but I haven't heard anything yet) that the minimum width of the Swatches panel in the default workspace is 17 instead of 16. The Swatches panel must be 16 swatches wide, otherwise the circular swatch pattern becomes slanted.
The culprit is the Layers panel which can't be as small as the Swatches panel, so if the Swatches panel and the Layers panel are put on the same column the Swatches panel will be wider to fit. The fix is to undock the swatches panel, at which point you can dock other panels below it that aren't wide.
Edit: I've created a new swatch set with shades instead of tints.
In the past I've used the VisiBone2 swatches in Photoshop, and I've been meaning to make an improved set of swatches for some time now, one that's organized like an actual color wheel. So I did. Here it is.
The special thing about this swatch layout is that the color wheel is actually accurate! It's not the VisiBone-style color wheel that uses red, green, and blue as the primary colors, where cyan is the complement of red. This uses the primary colors of pigments: red, yellow and blue, and displays it in full RGB gamut. It also takes into account that monitor green is not the same as reality green, and monitor blue is not the same as reality blue. So you can effectively use this as an accurate color wheel, making it great for working out color studies.
In the palette I've also included 3 value scales: simple grayscale, warm to cool, and cool to warm, which I use for my under paintings.
In the bottom right corner there's a small palette of colors that's already harmonized and CMYK safe for multipurpose use. I use that palette for line drawings, sketches, notes, and incidentally the Structure of Man Primer.
There's also a CMYK version of the color wheel (updated from the old one) if you plan on doing stuff for print. The ACO and ASE files are actual CMYK palettes, whereas the other ones are just CMYK safe RGB color palettes. So if you use that palette of colors you can be confident that the image you used them on will print predictable without having to work in CMYK mode because RGB mode performs better in Photoshop.
You can download the RGB and CMYK palettes here in multiple formats:
ACO Files (Adobe Photoshop Swatches)
RGB Color Wheel: ACO
CMYK Color Wheel: ACO
ASE Files (Adobe Swatch Exchange)
RGB Color Wheel: ASE
CMYK Color Wheel: ASE
RGB Color Wheel: ACT
CMYK Safe RGB Color Wheel: ACT
PAL Files (Jasc Swatches)
RGB Color Wheel: PAL
CMYK Safe RGB Color Wheel: PAL
TXT Files (Corel Painter Swatches)
RGB Color Wheel: TXT
CMYK Safe RGB Color Wheel: TXT