Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Batflat - Lightweight, fast, easy, and free CMS.
Anchor CMS - Free and lightweight blogging system
Shopping feed - Shopping feed is a versatile eCommerce application that allows eCommerce stores to thousands of channels.
Textpattern - Textpattern is an elegant content management system that is free, open source software.
ImpressPages CMS - ImpressPages is a PHP framework with admin panel.