Themes allow you to change the look and feel of your Drupal site. You can use themes contributed by others or create your own to share with the community. Contributed themes are not part of any official release and may not have optimized code/functionality for your purposes.
You can also create a sub-theme of an existing theme. A sub-theme inherits a parent theme's resources. Read more about Sub-theme structure and inheritance.
You can also view a full index of themes listing only their titles.
The theme has been tested in Firefox 14.0, Google Chrome 21.0, Chromium 18.0 (all in Ubuntu). The theme is fully XHTML and CSS compliant. Let us know the compatibilities in other browsers and we can update the list here.
The Alpha theme is being revived for Drupal 7 as a base theme for Omega, breaking out the "basic" functionality of Omega, so that in Omega 3.x you have the option between the "base" theme, and the power that you are familiar with by adding the Omega theme, and continuing to use that as you always have.
Midnight is a new theme that is mainly geared towards blogging. It has a user information bubble available for nodes and comments where information displayed is dependent on permissions like access profiles, access comments, display post information, etc. It comes with the option for two sidebars or just one. Both are displayed to the right of the content. It provides a default user picture unless something else is provided. The navigation is a region. There is also a region within the node, and a region below the content above the footer for whatever you can think to put there.
Using the XSL Engine and being a sub-theme of XSL Absolute starts XSL Bartik off with a lot of power behind it. With the page, node and comments already looking great thanks to the creators of Bartik you have a great looking site from the get-go. Then by using the power of XSLT in your theming engine allows you to customize easily and elegantly.
This theme was created for the same reason that many sub-themes were originally created – to make our own lives easier through creating a better starting point for themes that we build. Others have asked for something like this, so we're providing it here on Drupal.org to take advantage of community contributions, issue tracking, etc.