Autolab
course management and auto-grading of assignments
Canvas LMS
enterprise-grade learning management system
Danbooru
taggable image board
Feedbin
open-source feed reader for multiple platforms
GitLab
self hosted Git management
Helpful
simple and elegant support system
OpenFoodNetwork
software to manage the lifecycle of food
Open Source Billing
Beautifully Simple Billing Software
samson
Web interface for deployments
World Cube Association
everything for the World Cube Association
zammad
enterprise-ready helpdesk and customer support system