For publishers seeking additional revenue earning opportunities, Google AdSense consumer surveys may help.

When a user visits your site, they will have the option to answer a few survey questions in exchange for access to content. Each time a site visitor answers a survey question, you will earn $.05.
Highlights of Google Consumer Surveys include:

Earn $0.05 or local equivalent for each answered question

Easy to implement

You decide where and how surveys are shown

Survey prompt appears inline as visitor views content
Google AdSense Consumer Surveys Adds Additional Revenue Earning Opportunities For Publishers [adsense.blogspot.com]

Currently available in the US, UK, and Canada with plans to roll out to more countries soon.