Proxy for Google App Engine
SOCKS is not an HTTP-based protocol, so it's not possible to write a SOCKS proxy on App Engine.
Edit: Note I wrote the above when you were specifically referring to a SOCKS proxy.
Regarding general HTTP proxy servers, you can't really do that on App Engine, either, because proxies need to be able to accept requests for any hostname; your App Engine app will only accept requests for the hosts you're serving off it.
You could write an 'anonymizer' type interface on App Engine, but it's not a true proxy, because it will require rewriting URLs to work.
I am looking for a basic open source http proxy server for Google App Engine.
Preferably written in Python. Any suggestions?