These are some sites you can use to create assessments that are available from a variety of platforms and devices. They are all free.
Kahoot A”game based” student response system that students can access from any device with a web browser.
InfuseLearning A web based response system for web enabled devices.
Socrative Another web based response/quizzing system.
Plickers A fun tool for formative assessments when students don’t have devices or your network can’t handle a lot of traffic.
Poll Everywhere A quick survey tool that even includes an option for texts.