Open Educational Resources (OER): Polls and Scheduling Tools

Real time polling that allows users to text their keyword or code to vote. Includes Live PowerPoint polls, web responding, widgets, Twitter, downloadable results, and more. Free version allow unlimited polling with a maximum of 25 participants per poll.

Students share their understanding by answering formative assessment questions in a variety of formats: quizzes, quick question polls, exit tickets and space races. Once students join the teacher's room via the teacher's unique code.
Mobile versions (choose between teacher or student, then select your device).

Web based scheduling tool. Has three pricing tiers including free version. If you need customized branding or other premium benefits, ask for a 50% education discount (free version works fine for me).
Mobile versions:
Android       iTunes       Windows