SilverStrike is a Django webapp that you can use to manage your finances. Tries to make finance management easy. Heavily influenced by Firefly-iii (in particular the UI; both use AdminLTE) but tries to add some new features and leave out some less useful ones. Specifically supports multiple users accessing the same budget, i.e., a household. Supports multiple kinds of transactions (not just bill). Written in Python, uses Django. Has a REST API.
Perma.cc helps scholars, journals, courts, and others create permanent records of the web sources they cite. Perma.cc is simple, free to use, and is built and supported by libraries. Free to use at 10 records per month, unless you're an academic. Designed specifically so that it can be used for citations. Has an API. Open source. Written in Python, uses Django. Stores things as WARC files.
An offline version of the Khan Academy. Replicates the experience of the online classrooms. Watch videos, do exercises, track student progress. Can be customized. Use at home, in classrooms, or to create entire schools. Supports ten different languages now.