One Column Themes
TJ Clean is a simple, clean cut yet feature-full WordPress theme which is great for sites where content is king. Ideal for personal blogs as it includes integration with Flickr (photo sharing), Last.FM (music sharing) and status updates from Facebook/Twitter (and others). This theme is also XHTML Strict 1.0 and Valid CSS 2.1.
Two Column Themes
30April was created by the theme author to celebrate his birthday. This theme contains widget support, is fixed width, contains an extra footer, theme options to make changing and editing the theme easy and built in gravatar support.
Milky Conversations is a two column, widget ready theme that is based off of the White As Milk theme, written by Azeem Azeez. The theme has been released under GPL and is fully compliant with the license. As the name implies, this theme is pretty white with black text and a little bit of orange thrown in via the RSS icons.
Three Column Themes
Khaki Traveler was developed by Jeremy Clarke. It has a tan color scheme and a travel themed header. It is also a three column widget ready theme. It has gravatar support as well as tagging support. It has a top navigation menu with an easy to access log-in form.
Hybrid Themes – Themes Where The Number Of Columns Can Be Configured
Choice is a highly configurable theme that supports either 2 or 3 columns, is widgetized, theme options to control the themes background color, theme text weight, theme heading color, number of sidebars and whether or not your slogan appears. The theme also has native tag support.