Drupal s a world class, award-winning Content Management System, CMS. It is Open Source software, licensed under the GPL (General Public License) and therefore completely free to use. Below I have compiled a list of the most stunning free Drupal 6 themes in the community to-date. These are the best of the best and you won’t find better ones anywhere.

1. Acquia Prosper - Clean, good looking theme for an e-commerce website.

2. Compositio - Beautifully crafted blog theme from Design Disease. Designed to work with the Activity Stream and Tagadelic modules. 2 col only. Ported using the Genesis ULTRALITE starter subtheme.

3. BlogBuzz - Stunning Drupal theme! Everything is so clean, very well made. Could be a great theme for your portfolio web site or a blog.

4. Inove -  Compatible with Drupal 6

5. Morning After- This is a port of the Wordpress theme The Morning After to Drupal/ProsePoint, developed as a subtheme of Zen.

6. Magazeen - This bold magazine 2-col-theme was designed with the main focus being on typography, grids and magazine-look. It was created especially for Smashing Magazine and its readers.

7. Fusion Theme - Clean and simple theme which looks great!

8. Dark Elegance - Dark Elegance is a good looking dark background theme with a nice looking header. If you want to modify that for your taste a PSD of the header is provided.

9. Elements Theme - The design for the Elements Theme started as a design by Jason Schuller for his WP Elements website. Thankfully, Nicolas Borda ported the theme to Drupal for us.

10. Color Paper - Great piece of work! The best implementation of this theme could be for a blog or just a personal website.

11. Sky - This is a center aligned, CSS-based (no tables), multi-column layout theme, with some configurable color options, and support for many core configurations and some popular contributed modules.

12. Summertime - Summertime is a beautiful theme with lots of small fancy things which will make your Drupal website look unique.

13. Marinelli - Marinelli is a 3 column, tableless layout theme with a wide image banner and a “top-tabbed” primary-links system.

14. Black Mamba - Black Mamba is a heavy mod of the Waffles and Acquia Marina themes so credit goes to them. and you will see that in Black Mamba the header area is just as compact.

15. Mulpo - Mulpo is the new theme for mulpo.com. It is a simple clean theme with semantic markup, ideal for blogs. The mulpo theme manages to look very stylish with just one background image, all the rest is done with CSS.

16. 960 Robots - 960 Robots is a theme created by Lullabot for its Drupal theming videos and DVDs. This theme, based on the 960 grid system, features two columns on the right side of the page.

17. Novus - art of the AD Themes series, generously sponsored by Duplika, whereby some of the greatest themes for other content management systems, as well as general open source templates, are ported by Avioso Designs to Drupal.

18. Colourise - The original design is StyleShout's Colourise 1.0, awesome work from Erwin Aligam had modified text color scheme and typography to be more legible and more suitable for both Latin and Thai characters (my native).

19. Cleanfolio - Beautiful theme for a small and simple website.

20. RootCandy - This is very cool and great looking theme for Drupal’s administration section. Everything looks clean and shiny and those icons look awesome.

21. Ebizon RedFire - Ebizon RedFire is a strict xHTML validated, standards compliant CSS based drupal template with mission statement, breadcrumbs, custom footer.

22. Analytic - Clean modern theme with fine tuned css, will be great for blogs, communities.

23. Acquia Slate - Acquia Slate is an advanced, dark, corporate Drupal theme developed by TopNotchThemes in partnership with Acquia for their commercially-supported Drupal distribution.

24. Acquia Marina -  is an advanced theme developed by TopNotchThemes in partnership with Acquia for their commercially-supported Drupal distribution.

25. Worthapost - Addari is another clean theme contributed to Drupal from Worthapost.com. This theme targets those who want cleanliness and web 2.0 mixture for their Drupal based website.