A theme engine that allows you to use template files written in pure php. These template files do not need to be processed by the theme engine, and as such execute a lot faster than most other template engines. Another major advantage to using PHP as your template language, is flexibility, as the advanced user can access any information / functionality available in the Drupal API, and is not restricted to what the template engine / language allows him to do.
The 'default' template for this engine is box_grey_smarty, which is ported from the original box_grey theme.
Because of a drupal-contrib policy, a smarty installation is not currently included in default release tarballs. You can obtain a tarball already including Smarty in the libs directory here (4.6.x) or here (4.7.x).
Since Drupal 5, and even more so in Drupal 6 and beyond, the 'other' smarty theme engine (http://drupal.org/project/smarty) works much better. So there is no longer a need for wgSmarty, which is a good thing as it did confuse people anyway.
The XTemplate theme system uses templates to layout and style Web pages. It separates logic (PHP), structure (XHTML/HTML), and style (CSS), making it easy for designers to create or modify templates by working on XHTML/HTML and CSS without having to worry about any PHP coding.
This engine is compatible with both PHP 4 and 5 and is designed to be used with Drupal 4.7. I have no plans to update this module for 5.0. If someone would like to contribute a patch I'll be happy to review and commit it.
The Zengine theme engine is a CSS-oriented theme engine based entirely on PHPTemplate.
It is the continuation of the Zen theme project. Zen was designed to be a great starting theme, but this presented a problem because users who have already created their themes were unable to benefit from further development of the underlying Zen framework. Zengine attempts to solve the same issues as Zen in a more robust way which allows improvements to the underlying framework even for those who have already created their themes.
Awesomengine is the most awesome engine. It allows for embedding of PHP code, not only in html templates, but in css files, allowing for dynamically set CSS. Otherwise, it is nearly entirely identical to the phptemplate theme engine.
The XSL Engine supports XSLT processing for drupal templates. Now you can leverage the power of XPATH/XSLT for traversing your data. Quickly and elegantly format your semantic data structures into custom HTML markup in no time.
Peroxide is a Drupal theme engine allowing templates to be created using Haml and stylesheets to be written using Sass and Scss.
Templates and styles for large sites can become quite long and complex. The goal of this project is to make more advanced tools available to developers so that the code for themes is shorter, easier to understand and more maintainable.
Peroxide automatically compiles and caches templates as PHP. Sass and Scss files are also automatically compiled, cached and their resultant output css is automatically added to a page.
As far as I am aware, there is only one W3C specification to do with templating, and that's XSL-T. The bottom line is, you want to be able to use XSL for flexible output options. I hope to implement some way of switching between style sheet collections based on user agent or whatever.