If you've not done so already, it's worth signing up to YouGov. They are a survey company who periodically send notifications of surveys. They pay you for each one you complete. It typically takes a few minutes per survey, and you only get an email every few days or so.

These surveys are quoted on the news and in papers etc. They're also fed back to companies, essentially anyone who commissions a survey.

I've just done a 'brandindex' survey, it took about 2 minutes.