Markdown-paste is a project mainly written in Python, it's free.
Markdown paste site for Google App Engine
This is a simple, minimalistic anonymous paste site that runs on Google App Engine. It supports Markdown syntax for all pastes, and no other languages. It caches everything, and is fast.
Do whatever you want with it; it's public domain. You can see it running here:
http://mdpaste.appspot.com/