Openstack-cpp-client is a project mainly written in C++ and JAVASCRIPT, it's free.
A c++ client library for openstack
Works with Rackspace Cloud right now.
All it does at the moment is authenticate and print out the output.
API Docs: http://docs.rackspace.com/servers/api/v1.0/cs-devguide/content/index.html
To try it out on ubuntu:
sudo apt-get install libboost-system-dev libasio-dev openssl-dev xerces-c-dev xsdcxx ./build.sh ./test API_USERNAME API_KEY