Kahoot is a different type of web-based Student Response System. While most student response systems just pop up questions for students to answer via their devices, Kahoot takes the quiz game approach. Students become actively engaged in the questions and compete to get the correct responses.
Check out this video and the link below to give Kahoot a try.
Geddit is a new web based tool for getting feedback from students a for performing formative assessments during lessons. Students can use any web enabled device from classroom computers / laptops to tablets & phones.
Check out Geddit here. Be sure to run through the online demo lesson to get a good understanding of how their system works.