Infuse learning and Socrative teacher are both free and easy to use formative assessment software tools. Teachers create accounts and are assigned a room number. That room number never changes, so it makes it easy for kids to know what room to go to. They can be posted in the room for easy viewing (usually a five digit number).
Now the fun begins. You have students go to the student signin/login page for each site. They put their name and the room number and then the page opens. When it first opens, it states that it is waiting on the next question. The teacher then asks, shows, projects, or explains the question and the teacher picks the type of answer they want. Students then see that type of answer box appear on their device and then they respond. Both systems record answers and show you class average, individual answers, and more.
Now, the best part about Socrative is that it never froze and it worked without a hitch. I did not like the lack of options on questions: Only allowed multiple choice, true or false, and short answer. The pre-made exit pass was a big plus. It already was created and allowed me to get feedback at the end of the lesson without making up an exit pass. Nice feature and you can choose how to save the answers (note in slideshow).
Both offered to allow you to upload quizzes. That is a nice option, self graded (but I think I will continue to use Quizstar for that).
In the end, both are cool and worth a look. I would side toward Infuse learning because of all the options, but the glitch of it freezing up might push me away. Socrative is no joke and gets the job done.
Let me know what you like and how they work for you.