Streamie – Open Source & Real-Time Twitter Client
Streamie is a web-based, totally real-time and open source Twitter client which makes use of the latest web standards such as HTML5 and CSS3.
It has different menus for displaying mentions, direct messages, favorites or retweets. And, as expected, you can send tweets easily.
A number of options help customizing the application like message filtering, display settings and enabling geolocation.
The application is fully Ajaxed + uses nodeJS, less.js, require.js and Socket.IO which can be a good way of getting experienced in these "getting popular" resources.