A new Drupal community contribution, the Dichotomy theme:

This layout uses a central column with a main region, two right sidebar regions, and a footer region that allows for horizontal stacking of blocks.

Originally distributed with a colour palette of strong green and gray: http://drupal.org/project/dichotomy. The theme is now available in all four flavours shown above (green, pink, blue, and orange): dichotomy.zip.

n.b. The theme has been tested successfully on WinXP Firefox 2.x, Internet Explorer 6 & 7, but has known alignment issues on Linux Firefox 2.