Many big companies are looking for feedback about the usability of their website.
This is where Usertesting.com comes in. You sign up for free and then answer questions about a particular website, explaining what is good or bad, confusing or clear, etc. and then you get paid.
You have to be accepted into the program and must be 18+, but the payouts are pretty good! Their current payouts are $10-$15 per test and the tests normally take about 20 minutes.
I found the video below from a tester explaining how it works.
