To experiment a little with automatic trading I'm looking for a trading api (like mtgox has) which is used on multiple independent websites so that if one goes under that I then don't have to redo my whole program. If possible one from open source bitcoin trading websites so that I can setup one in a vm and use that to test against.
I'm currently running my tests against Mt.Gox but that can be a bit expensive when the script doesn't perform too well.
The Java XChange library could help
It might not be exactly what you're after, but the XChange project provides a demonstration of a general purpose API for communicating with multiple exchanges.
You could repurpose the code to create your own mock trading endpoints and run up a collection of virtual hosts. In this manner you can test against a reasonably well known set of APIs for the usual failure modes.
goxcli could also be an interesting codebase to make your own multi exchange trading api, goxcli provides an interesting and a shell api you can use as a backend to build your own frontend on top of it. for no goxcli supports only mtgox, but its open source and you can fork it on github : https://github.com/Trasp/GoxCLI
see also : https://github.com/neofutur/bitcoin_simple_php_tools
