Hi,
Obviously I am gonna say ours: phpAuction. We had launched a month ago a full new development: enuuk Auction platform with:
* Pages follow XHTML 1.0 Strict specification - All the pages are prepared for current and future browsers
* PHP5 object oriented code - Now the code is more professional, and is separated in functionality modules: that means it's easier to expand it, to tweak it to match your needs, and it's faster to debug in case you found a bug.
* MVC pattern - The data can be presented to the user in different ways, so each page is virtually prepared to be seen in normal HTML, but also in RSS, Ajax JSON, WAP, etc... just name it! Moreover this implies easy integration with other web tools like CMS (Drupal, Wordpress), or even desktop applications.
* Internationalization with standard .po files (gettext platform) - Now you can easily add a new language to the web just using a nice application like poEdit. No more need to explore all files looking for sentences in English to translate; all translations reside in a single file.
* Auto-testing system with PHPUnit - the core system has a collection of code tests that assure that, if somebody changes a line of code, the core system still works at it's expected to work.
* PEAR PHP Coding Standards - Strictly following these standards make the source code more legible, with a full documentation in comments, so any professional programmer can easily understand it.
* jQuery - This javascript library allow us to create a wide variety of visual effects, useful and impressive at the same time, like fast sortable tables or fadeout messages.
I invite you to check it at:
http://www.phpauction.net/enuuk-auction-platform/
L