Some things I've created, maintain or participate in in some fashion:

Gabbi

Declarative testing of HTTP APIs.

TiddlyWeb

The canonical HTTP API for tiddlers: small chunks of content on the web.

Tank

A flexible wiki and application platform built on TiddlyWeb.

Purplewiki

A wiki implementing Purple Numbers for granular addressability and transclusion. Long dead but the foundation on which a concept known as PurpleUniverse was built: 15 years later still the best collaborative environment I've ever worked with.

OpenStack

I'm "core" in a few projects in OpenStack: open source software for creating and managing cloud infrastructure and services.

wsgi-intercept

Test WSGI applications with real http clients without a server.