Where is it: www.socrative.com

Update coming - Socrative has been purchased by MasteryConnect (announced June 23)

What it is: A web based response system: It allows students to use any web device (phones, tablets, etc.) to respond to prompts from teachers. For example, a teacher can verbally ask the class a question, and the students respond via their phones. The teacher gets an instant response and can see how many got the answer correct. This allows for a quick check for understanding. Responses are recorded in a Google Docs spreadsheet and may then be used for part of a grade. 

How does it work: This is a variation of the ""clickers"", but without the devices. Students use their phone or other web device to answer a single question which can be Multiple choice, True/False, or Short Answer. Exit Tickets, and full quizzes are also supported. The Questions need to be created in advance, and the class is given a specific ""Room Number"" (all students get the same room number)  to enter at a student site (m.socrative.com). When responding, students get a screen to enter their name so the answers can be associated to the student. Teachers can see the answers as the students complete the question(s), and save the results for later grade collection.

What data do they collect:  It varies on who you are: Students don't have to sign up for an account, so they disclose limited information to respond to quizzes. (They enter a ""room number"" given by their teacher.) Teachers must have an account which requires at least an email address, and they ask for the reason for your usage. They do not disclose information to third parties, but may have links to other sites that they do not control, and their policies may differ. 

How well does it work:I cannot speak first hand as I have not tried the service. One university professor I have spoken to, and who uses it, states that it is very useful for doing a check of understanding. 

How do they support the site: The site is currently in a Beta (testing) stage. In the Terms Of Service, there is mention that when the Beta is complete, all accounts may convert to a commercial account. You will have the right to delete your account at that time if you do not wish to continue with the new service.