File sharing + sync, notes, and photos (alternative to Nextcloud and ownCloud's RSS reader).
Photo and video backup solution directly from your mobile phone (alternative to Google Photos).
Syncthing is an open source peer-to-peer file synchronisation tool.
Knowledge base that works with a SQLite db file.
Note taking application with markdown editor and encryption support for mobile and desktop platforms. Runs client-side and syncs through a self hosted Nextcloud instance or similar (alternative to Evernote).
Easy to use, and extensible RSS feed aggregator capable of generating RSS feeds from pretty much everything ranging from social media to university departments.
Web-based operating system designed to be feature-rich, exceptionally fast, and highly extensible.