Crayon World is a clean theme with a colorful header.

Prebuilt is a simple red and white theme for WordPress. It has a top menu bar, relatively wide right side bar and an extended footer with Flickr integration.

From the site:

Prebuilt was created not to be heavily graphical and feature a lot of ajax goodness, but to be effective while at the same time, an easy way of learning Wordpress.

From the site:

Jentri is a smart and sophisticated theme developed for WordPress.

Includes a 7 color switcher and a custom style sheet switcher versions.

From the site:

Impact is a free WordPress(1.5) theme - fast-loading, with a minimum of images and scope for customisation. The work has gone in to making it simple, both in appearance and code.