Online demo: http://thewall.agilityjs.com
The Wall is an Agility.js example app. It lets anyone write on a virtual wall, anonymously.
The entire browser-side code is under:
public/app.js
Node.js is used for the backend, MongoDB for the data store, and the Skeleton boilerplate to make things look pretty.
To start the server you'll need node.js and a MongoDB server. Run:
cd thewall/
npm install
node server.js
That's all. Have fun!