If you want to ask a question of your class or just poll them for a response, you don't need to worry about passing out clickers. you can you a free tools called Naiku http://www.naiku.net/quickquestion/ The instructions are fairly simple, create an account, select a questions type, tell your students to direct their browser to the link provided, and ask your question. Pretty cool!
Socrative is another free web app that allows students to use netbooks or other mobile devices in place of clickers. Students may download the app to the smartphone, access assessments over the web and also set up accounts to develop their own assessments.