Twibes is a great tool to enhance students collaboration on Twitter. It allows users to either create their own discussion groups or join existing groups to discuss topics around a particular area.
Hark is the world’s platform for sound bites, where anyone can discover, create, play and share their favorite audio moments anywhere on any device through digital embedding, or via social networks such as Facebook, Twitter or Google+. Using Hark you will be able to upload sound bites and add them to your Tweets.
Twijector is a free online service for webcasting tweets regarding various events. Using Twijector you will be able to create a real-time Twitter wall that you can project in your classroom . It also allows you to keep track of live tweet-streams of a particular event, hashtag or keyword.