cal.com : Open source meeting scheduling tool. Send a link, let others book a slot. Calendly alternative.
Zulip : Powerful slack-like open source group chat
Commento : A lightweight, open source, tracking-free comment engine alternative to Disqus.
ProjectPier.org : ProjectPier is a Free, Open-Source, PHP application for managing tasks, projects and teams through an intuitive web interface. It must be downloaded a...
Kinto : Kinto is a lightweight JSON storage service with synchronisation and sharing abilities.
A free, hosted, portable and open source photo sharing service. A photo application that lets you store your photos on Dropbox, Amazon S3 or in your garage.