Here's a list of starter themes that I have observed popular. The first three would be the ones that I've tried out. The next ones are the ones I am planning to try out. Below the names of each theme are the description taken directly from their project page:
For many people, Zen is the ultimate starting theme for Drupal. If you are building your own standards-compliant theme, you will find it much easier to start with Zen than to start with Garland or Bluemarine. This theme has LOTs of documentation in the form of code comments for both the PHP (template.php) and HTML (page.tpl.php, node.tpl.php).
Genesis is an standards compliant, accessible and semantically rich starter theme for Drupal. Genesis is easy to theme yet extremely flexible, giving you endless theming possibilities. Genesis makes building a standards compliant accessible theme easier than starting from scratch.
This is a liquid layout theme that handles layout for one, two, and three columns based on which blocks are enabled using CSS, not tables. There is not a lot of "pretty" in this theme as it is meant to be used as a starting point for theme creators to customize with their own look and feel.
It does include one extra region to place blocks above the page content, as well as below it.
Fusion is a powerful base theme, with layout and style configuration options built in that you can control through Drupal's UI. It's based on a simplified 960px or fluid 16-column grid. It's designed to be used with the Skinr module, with numerous useful block styles included.
Don't theme yourself into a corner. Our goal is to make Fusion the clear, simple, and supported option for creating advanced Drupal themes.
Adaptivetheme is a mega-powerful starter theme with tonnes of layout and site configuration options - its dead easy to customize using the 80+ theme settings and the amazing Skinr module. The output is super clean and a lot of work has gone into generating lightweight, semantically rich HTML. Its also content source ordered (content first, sidebars second).
Blueprint is a starter Drupal theme meant to make development of custom themes faster.
Features
- Normalizes Drupal’s CSS to be consistent.
- Properly aggregates all Blueprint CSS files into a single file when this setting is enabled.
- Put scripts at bottom of page for nice performance gains.
- Flexible layout, from 1 to 3 columns, based on where you configure your blocks to show (left, center, right).
- SEO optimization without the need for heavy modules and additional queries per page.
- Better forum icons.
- Improve forum display and performance.
- Prevents duplicate form submissions with jQuery, read more.
- Shows the # of comments below a node since Drupal doesn’t do this by default (usability).
- Add permalinks to each comment.
- Highlight any comments by the author of the node.
- Adds a “you need to login / register” box below all comments if you can’t add a comment (usability).
- Supports conditional comment subjects, if the setting is off it won’t show a chopped off title of the comment.
- Uses CSSEdit comments for grouping of styles.
- Lots of comments and theming tricks in template.php to learn from.
This theme is based on the 960 Grid System. Details on its background can be found in a journal entry by Nathan Smith.
NineSixty is a base theme with all the files provided by the 960 Grid System. From the sketch sheets to all the styles from the framework are included. There are a few modifications so it better fits into Drupal. All the details are inside the README.txt file.
Any modifications should be done from sub-themes. All that's needed is a "base theme" entry within your sub-theme's .info file pointing to "ninesixty". For example, base theme = ninesixty.
It is not simply a grid based layout system. It helps workflow by allowing better communication between developers, information architects, visual designers or anyone involved. The sketch sheet can be used for the rough initial designs by the visual designer. Meanwhile the OmniGraffle and Visio templates can be used by the IA. From there the Photoshop and Fireworks templates are provided to refine the sites graphics and layout. From start to finish with all sides involved, this helps everyone share a common visual language.
Even if you are the only one developing a site. The simple layout system is very easy to implement freeing you to other more important tasks.
If you wish for a more comprehensive list, you might want to check out this page.