Courseroot - Biggest online course database on the web
Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Alcamy - Free, open self-learning platform. Learn & teach anything.
Anchor CMS - Free and lightweight blogging system
CurrencyStack - A free modern currency data API for fintech apps.
Textpattern - Textpattern is an elegant content management system that is free, open source software.