http://www.polleverywhere.com/

Poll everywhere gives teachers the ability to post polls in real time.  All students can answer questions at the same time.  This is an interactive way to involve all students.  Things to consider are; only 30 respondents are available for the free subscription, check with students to verify text messaging is included in their plans and that your school district allows cell phones to be used in school.  Your account can move with you if you relocate to other countries.  Polls are private, can be downloaded as powerpoint slides and may be imbedded in powerpoints for use during keynote speaking.  There is an option to allow for voting over the web which involves emailing the URL of the question to each student for their responses.

When graphs are to be displayed there is a template which allows for customization of the backgrounds and color of text.