Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Courseroot - Biggest online course database on the web
Anchor CMS - Free and lightweight blogging system
Alcamy - Free, open self-learning platform. Learn & teach anything.
Textpattern - Textpattern is an elegant content management system that is free, open source software.
Startup Stash - A curated directory of 400 resources & tools for startups