Classroom voting is a way to collect and aggregate a student responses to a question. The responses can be used to encourage further discussion and/or to guide the next step in a lecture.
Carl Weiman Science Education Initiative: When Carl Weiman won the Nobel Prize in physics, he devoted a portion of his prize money to improving physics instruction. An early focus was on using classroom response systems productively. They developed a large research base and a set of best practices, which are shared on this site
MathQuest/MathVote at Carrol College: Math QUEST and MathVote were NSF-funded projects to explore classroom response systems in college mathematics. The project led to a number of resources, including published research, a huge question library, and a book published by the MAA—all of which are available at the site. (Note, the link to the book on the webstie is broken, see below for an updated link)
Agile Learning: Clickers. Derek Bruff's site, with a collection of blog posts related to clicker use
See this page for question libraies sorted by course
Fred's favorite: Plickers (Completely free, low-tech, and so easy to use. Students don't need any technology. They hold up cards, and the teacher scans the room with a cell phone to collect votes. Up too 100 votes at a time)
Others:
Peardeck (add on for Google slides that allows for a variety of response methods, including multiple choice, text entry, and drawing)
Plickers (completely free and low-tech. Students hold up cards, teacher scans the room with a cell phone to collect votes. Up too 100 votes at a time)
Poll everywhere (students respond via cell phone or internet device—app, web, or text. Free plan is limited to 40 responses per poll)
Slido (students respond using a phone or browser. Free plan is limited to 100 partiicpants and 3 polls per event)
Socrative (web- or app-based. Up to 50 responses per poll for the free version)
"Analog" clickers: colored paper
Remote engagement: For online courses conducted via synchronous video, many platforms include an option to poll participants:
You can also use Google Forms to create and share polls online