I found Apigee's API design eBook really useful: http://apigee.com/about/resources/ebooks/web-api-design http://apigee.com/about/resources/ebooks/web-api-desig

I found Apigee's API design eBook really useful: http://apigee.com/about/resources/ebooks/web-api-design http://apigee.com/about/resources/ebooks/web-api-design I was impressed with the Rackspace Cloud API and documentation too. Especially their authentication services.