Notes:
To let users do creative stuff with your service, you need to provide them with a programming interface that exposes the same content available to human users. For example, amazon lets you access their database with URIs that look like this. This is quite a contrast to traditional heavy duty web services built with SOAP and WSDL. Its actually very close to what is called REST web services (Representational State Transfer). Although REST experts would argue that a URI with verbs in it is not RESTful. But for purposes of facilitating mashups, RESTfulness may not be a top priority.