Pinecone Research is a great company to join to earn a little extra cash. They pay $3 per completed survey. They use the surveys to help their advertisers get the information they need. I have been a member for a few years and it only takes about 15 minutes to complete each survey. This is a legitimate company and they pay quickly.
They only take new members for very limited times and right now they are looking for women ages 18-24 or age 35+.