Some tools to consider:

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Blackboard Collaborate has real-time polling features

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Poll Everywhere -- real-time polling

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From DSC:
By the way, faith-based organizations might want to consider using this tool as well.  Also, my thanks to Professor Randall Pruim, in the Mathematics Department at Calvin College, for bringing the options below to my attention. Note: Professor Pruim doesn’t necessarily recommend these tools — as both SMS Poll and Lecturetools.com require that students pay a subscription. However, I list these tools here in case you want to compare functionality/pricing/etc.

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smspoll.net -- real time polling of your students

 

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http://www.lecturetools.com/

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Addendum on 2/2/12:

 

socrative.com -- engage the class using any device

NOTE:  Randy mentioned that Socrative requires access to the Internet (laptop or smart phone); there is no cell phone interface at this time. So you must have a web-enabled device.

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Addendum on 2/21/12:

 

Addendum on 7/18/12:

TopHatMonocle.com
A web based clicker and online homework tool; polls and quizzes

No clickers to buy! Students can use any device to participate in class

  • For in-class and homework use
  • Questions, open ended discussions and interactive demos
  • Use with any presentation software, such as PowerPoint
  • Amazingly simple! Takes minutes to setup

 

Addendum on 11/15/12:

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