I was playing with requests, a nicer http library for Python, and I wanted to see how it handled the various HTTP responses. I can't remember how but luckily I found exactly what I needed on httpbin.org.
From their website:
httpbin(1): HTTP Request & Response Service
Testing an HTTP Library can become difficult sometimes. PostBin.org is fantastic for testing POST requests, but not much else. This exists to cover all kinds of HTTP scenarios. Additional endpoints are being considered (e.g. /deflate).
All endpoint responses are JSON-encoded.