nessus-xmlrpc is a Ruby library for the Nessus XML-RPC interface. You can use it to start, stop, pause, and resume scans. It lets you watch progress and status of scans, download reports, etc. It comes with an example command line program that shows how easy it is to interact with the Nessus scanner.
PyMetasploit is a full-fledged msfrpc client library for the Metasploit server (msfrpcd). The library features an easy-to-use object-oriented approach to accessing all the features available within the Metasploit framework. With only a few simple lines of code, developers can select exploit/payload/auxiliary modules, configure them, and execute them.
JsonRpcPhp is a class that sends HTTP requests to a given JSON RPC server to call a specified function, passing any additional parameters. It can also send multiple JSON RPC requests and return the results of all calls. Another class can process server requests by registering a given object of service class and dispatching requests to be handled by that object.