Just finished up a 4-column theme for WP 1.5+ called News Time.
It has 3 main columns where the posts go - you can select the order to be:
-) left to right then repeat, or
-) 3 categories, one for each column, or
-) equally posted, first the left col, then middle, then right
The fourth column on the right is for search, advertising, links and so on. There is a README.txt that comes with the release that explains it.