Mentimeter

Interact with your audience by having them respond to a multiple choice question via their mobile device.
http://mentimeter.com/

To Vote

1. Go to m.mentimeter.com
2. Enter the Vote ID

Vote ID - 71756

Sweet

Post link to live results via Twitter/Facebook - Here's a link to our results: http://mentimeter.com/public/1f84b9d5cd9b
Infinite number of questions
Results can be embedded into your blog or wiki - See for yourself: http://chasingweb20.blogspot.com/2012/02/mentimeter.html
Questions are saved forever!

Bummer

You can't create a series of questions
There is no login to save your questions. You're going to have to remember your Vote ID and results URL.