habanero is a simple CMS that I wrote using PHP, MySQL, XHTML and CSS. By conforming to web standards it produces valid accessible output. The cheesey strapline for habanero is a little goes a long way.
It enabled me to build a handful of similar sites quickly, and includes features such as a calendar, links and media libraries, a gallery, a guestbook, clean URLs, support for Google Analytics, an in-place database schema update system (to allow sites that are already up and running to get software updates) and an admin interface with a WYSIWYG editor, a contextual help system, and style controls incorporating a colour picker to enable the webmaster to change the appearance of the site without writing any code.
There are a few comments in the code which suggest I started habaenero around 2005. There are still a few sites out there ticking along quite happily on the CMS, but it's not a project under active development any more.