Poll Everywhere is a website which allows you to set up a poll which can be taken by anyone you give a link to.

The poll can be taken using a mobile device or a computer and results are updated live.  You can even embed the live poll in a powerpoint slide if you want it to be part of a presentation.

To set up a poll for free go to this website: http://www.polleverywhere.com/.  For a tutorial watch the video below:
 
If you have set up a Google Documents Account you can create a Google Form.  A Google Form allows you to pose questions and accept answers.  Not only can you see the answers that users have given but Google Forms also puts these into nice neat little charts for you to give you an overview of results.

You could use this great tool to set up simple polls which students can access on their devices and then look at the live results in a lesson.

Here is a video tutorial.  Go ahead and watch it!
If you are not sure how to set up a Google Account just go to www.google.com. Sign up for an account and you will automatically have Google Documents.  You may wish to ask your ICT Coordinator to explore the possibility of a Google Apps for Education Account if you don't already have one to give everyone in your institution access to these great tools.
Example of Use:

Our business department have used Google Forms to allow students to carry out market analysis.  As part of a challenge where they had to design and market a pizza they produced a survey and used the results to influence their design and their marketing campaign. 

The group chosen as having the best promotional campaign incidentally got to make the pizza at the local dominoes show, use the promotional material they had produced and the pizza was on sale for a week!