Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.

Ushahidi - Ushahidi gathers data from various sources and reports incidences around the world in real time.

Anchor CMS - Free and lightweight blogging system

neptunes. - We help both listeners and musicians to find each other.

Textpattern - Textpattern is an elegant content management system that is free, open source software.

Startup Escape - A real-life startup themed escape room in SF!