MockMockWeb is a Heroku-ready Node.js-based Web application server which allows you to mock up a website in seconds. It allows you to instantly launch a website which sends an empty page (with status 200) to any request/URL and edit any page on the spot. You can also edit the layout shared throughout your website. It lets you build a mock (sometimes real) website in a request-driven interaction.
msg-rpc provides bidirectional RPC support over a simple message interface such as WebSocket. Tere are WebSocket examples based on socket.io and sockjs. It just has a simple sendMessage/onMessage interface, with no other dependencies. It supports not only normal RPC, but also RPC Service, which makes RPC pushable (i.e. the server can also send a request to the client and expect some kind of response).