Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
gitsome - Supercharged Git/Shell autocompleter w/ GitHub integration
httpbin(1) - HTTP request and response service
Moving to HTTPS Guide - A community site to help site owners migrate to HTTPS
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.
Endpoints - View and respond to requests on an HTTP endpoint