Alaveteli
easy FOIA requests for any jurisdiction
brief-ideas
journal for brief ideas
Brimir
an email helpdesk
CircuitVerse.org
circuit simulator
CodeTriage
directory of open-source projects with open issues
Cuttlefish
a good-enough SMTP server so you can ditch SMTP providers
Diaspora
community-run, distributed social-network
Droptune
music notifications for Spotify and Apple Music
Expertiza
peer-reviews app, supported by the National Science Foundation
Fat Free CRM
a clean, customizable CRM
FederalRegister.gov
daily journal for the United States Government
Feedbin
open-source feed reader for multiple platforms
fromthepage.com
crowdsource handwritten documents
Growstuff
tool for small-scale food growers
iNaturalist.org
social network for nature stuff
Juvia
commenting server of the likes of Discus or IntenseDebate
LearnAwesome.org
social network of learners
Notebook Gallery
enterprise Jupyter notebook sharing and collaboration platform
OneBody
church management software
OpenProject
project management system
openSNP
annotate your SNP-set
Open Split Time
endurance event data management
Organization for Transformative Works Archive
archives of fanworks, including fanfic, fanart, and fan vids
PublicLab.org
collaborative knowledge-exchange platform
Racing On Rails
bike racing association management
sharetribe
Marketplace platform
Skyderby
flight analysis and competition scoring
TagTeam
social tagging for academics
Teambox
the original teambox.com
Tracks
software for implementing David Allen's Getting Things Done™ methodology
va.gov
API for va.gov
WikiEduDashboard
course dashboard system