Piazza is a free online gathering place where students can ask, answer, and explore 24/7, under the guidance of their instructors. Students as well as instructors can answer questions, fueling a healthy, collaborative discussion.
Purdue has developed and deployed a large suite of digital technologies designed to improve student success. They developed this tool - Mixable, that enables informaiton to be delivered though a mobile device, Facebook application, or web browser. All these technologies are designed to connect the classroom with the class using the connections and devices common to students such as dropbox, video/image sharing tool, etc.
Here is the description from Edmodo: "Edmodo provides a safe and easy way for your class to connect and collaborate, share content, and access homework, grades and school notices. Our goal is to help educators harness the power of social media to customize the classroom for each and every learner." Is it another Blackboard? Or not? A feature for this tool is that you can choose to get mobile notifications of updates from the teacher.