Butcher Trays: I like to use a butcher tray when I'm painting some of my more spontaneous work. The paint is always fresh. Mixing is easy. Colors flow together to create new colors. Its easy to make big puddles of color. And finally, the color used in the painting flows to the sides of the tray and creates lovely neutrals based on the color used in the painting.
Stephen Quiller Color Wheel Palette: This is my favorite everyday use palette. It has wells for colors arranged in a color wheel with 12 wedges. It helps me remember what I know about color theory and I have an immediate idea of what every color is on the wheel. This palette also helps me mix grays and has some little wells for off colors.
There are also several other square type palettes. From workshops with other artists I've found some arrange the color according to value with the darks on one side and the lighter color on the other. Another artist I know arranges the palette according to warm and cool color.
Any of these work well according to the way in which you want to work. While I prefer the top two above, I can certainly see lots of merit in other arrangements. The final word is to experiment and find what works for you.