CodeCuriosity.org
platform to reward OSS contributors
CodeTriage
directory of open-source projects with open issues
Diaspora
community-run, distributed social-network
Discourse
next-generation discussion platform
Ekylibre
farm management information system
exercism.io
code practice and mentorship
Feedbin
open-source feed reader for multiple platforms
GitLab
self hosted Git management
GitLab CI
continuous integration server
Helpy
A Modern Helpdesk Alternative
Lewsnetter
email marketing application
Octobox
GitHub notification manager
Open Build Service
build service for Linux packages
openSNP
annotate your SNP-set
openstreetmap.org
crowd-sourced map of the world
Organization for Transformative Works Archive
archives of fanworks, including fanfic, fanart, and fan vids
Racing On Rails
bike racing association management
Registry
TLD management software
rubygems.org
The Ruby community's gem hosting service
Sanataro
household accounting software
whitehall
government content publishing for gov.uk
Wreeto
note-taking, knowledge management, and wiki