I don't have time to write a detailed tutorial on this much requested topic but here's the basics.In sidebar.php:
Make 2 sidebar divs instead of one as follows:
1. Replace the word 'sidebar' in the div tag with 'sidebar1' and make the function say dynamic_sidebar('sidebar1') instead of dynamic_sidebar('sidebar')
2. Copy this new edited entire sidebar.php file and paste it below the original.
3. Replace the two occurrences of 'sidebar1' with 'sidebar2' in the second half.In index.php:
Move the get_sidebar function so that it is before the main content but after the header.In style.css:
Change the name of all the 'sidebar' references to 'sidebar1'
Duplicate all the sidebar1 lines and call the copies sidebar2
Make sidebar1 float left and make sidebar2 floar right.
Add a large left margin and right margin to the to the main content so that the sidebars fit each side.
I just did this to my site at http://dubbo.org
and it worked fine - you can see it there.
It's basically the same theme but without the sliding doors.