Light Folio
Light Folio is a clean clean and light theme with a combination black and white color.
CleanTech
CleanTech is a clean, two column and elegant theme with support for threaded comments designed to focus your content.
Ultima
This is a 2-column, soft-colored, rounded theme that totally aims at content and nothing else.
More at: http://weblogtoolscollection.com/archives/2010/03/03/wordpress-theme-releases-for-0303-2/