Multipurpose RTL-SDR Framework for RTL2832 based DVB-T receivers. a Flask-SocketIO based Web interface which houses it's features there. Web interface preferred to the command line interface for facilitating the usage and supporting remote operations. Has some graphical capabilities through Matplotlib.
A REST API for the double-entry bookkeeping software beancount.
Baresip is a portable and modular SIP User-Agent with audio and video support. Tries to be a Swiss Army knife for SIP and VoIP. Supports encryption. Has an embedded web server with an HTTP (REST?) API for controlling the utility. Modular architecture.
MusicBrainz open sourced their scrobbling server. Implements the last.fm scrobbling API. Uses Google BigQuery to calculate statistics on a schedule. I don't see why you couldn't stand it up without Docker. Written in Python. Requires Postgres.
Osmedeus allow you automated run the collection of awesome tools to reconnaissance and vulnerability scanning against the target. Webapp, uses Flask. Has a REST API.
put.io is a service that takes care of downloading most of the things.
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.
A company that integrates with banks and financial institutions and provides an API when said institutions don't. Some fairly prominent companies seem to use them (Betterment, Venmo, Coinbase, Fanny Mae, AmEx). Intended for helping users budget, manage payments, and bookkeeping.
API docs: https://plaid.com/docs/
A web application made to ease shared budget management. It keeps track of who bought what, when, and for whom; and helps to settle the bills. Written in Python, uses a database (MySQL, Postgres, SQLite) as its back-end. Can be installed as a first-class Pip module. Has a REST API, of course.
A collective list of free APIs for use in software and web development.
A fast and easy file sharing application. Upload a file and it generates a unique link (even for duplicates). Send the link to someone and they can download the file with it. You can set a password on the site to control who can use it. Links can be set to self-destruct. No database required, just PHP. Encryption optional. Cronjob to delete old files. Comes with a PoC bash script for uploading from the command line.
A web application that sits in front of a command line Signal client that lets you send messages from a web browser. Seems to also have a REST API. Requires a second phone number to set up an account, it's not an extension to an existing Signal setup. Looks like all-Docker-all-the-time but it looks like you can also run it as a system service (a systemd .service file is in the docs, and it says nothing about using Docker for that).
Interestingly, it's a couple of shell scripts.
A site that exposes an API which tracks global CO2 levels.
MusicBrainz is an open music encyclopedia that collects music metadata and makes it available to the public.
YaCy's wiki, caught by the Wayback Machine.
Builds Reusable Objects for Consuming Web APIs. Works with Requests, aiohttp, and Twisted. Basically, turn an HTTP API into a Python class.
A collection of applications able to interact with websites, without requiring the user to open them in a browser. It also provides well-defined APIs to talk to websites lacking one. Automate access and extraction of data from websites that don't make it easy or possible. Has applications for adding accessibility to sites that are unfriendly to the visually impaired. Tries to focus on quality of results. Multiple interfaces.
United States Postal Service APIs. I should be able to plug this into Switchboard.