REST is the most commonly used technology for calling services. For an overview of REST, you can read An Introduction to RESTful Services and More on REST but briefly, REST services are located through their unique URIs and use standard HTTP commands like GET, POST, PUT, and DELETE to interact with the service. Because they are based on HTTP, REST services can be accessed from a broad set of platforms. In some cases, language specific libraries can abstract out some details and simplify calling REST services. Language specific Azure SDKs and tools for the platform of your choice can be found on the Microsoft Azure Downloads page.