I've been promising (threatening) to do this for a while, so I took some time out to get it kick started over the last few weeks. It's based on the enormous success of the "Sliced Bread php Snippets" idea, which has grown considerably since it started in 2005.
It's a new approach to how themes and layouts are contributed to Drupal and is based on the following assumptions:
There are very few themes being contributed to Drupal compared to modules
Drupallers may not have the time to contribute their themes
Drupallers may feel nervous about many people using their themes and every site looking the same as theirs
Drupallers might prefer to have a distinctive and exclusive design/layout. (illustrated well by the responses to "Why can't I get the drupal.org theme?")
It's quite a job to prepare a full theme for distribution - because of the sheer depth and dimensions to Drupal, it's not just a "skin" that is needed, it's a collection of themes that covers the front, blogs, lists, admin, comments, nodes etc.
The first thing Drupallers do when they download a theme, is strip it apart
It's much easier for Drupallers to contribute theme and layout snippets rather than full themes
Modular based theming
Drupal is 5 years old and it's incorrectly compared by some to other blogging or CMS tools where only a "skin" is really needed. The depth and dimensions to a Drupal site means a "skin" is not enough. I would argue that it is a collection of skins for specific areas and therefore it is difficult to expect the THEME DOWNLOADs section of the site to be just as populated as other sites.
I am trying to implement an table-free theme based on the Pushbutton theme using Skidoo's Ruthsarian Layouts (http://webhost.bridgew.edu/etribou/layouts/skidoo/). It works fine in Firefox and Opera, and validates as true XHTML 1.0 Transitional. But in Internet Explorer 6 there are bugs: You can't highlight (and copy) text, some borders and images disappears.
If anybody is interested, I would be glad to contribute this theme variation.
One thing I had trouble with was the font in the header of the main block. I wanted it to be white against the blue background, but couldn't figure out how to do it. If anybody can give me a clue, please post.