UserTesting has been an amazing way to earn a little extra cash in the two years I've been a tester. The tests are not difficult and are pretty fun most of the time (learning about a new upcoming product, thinking critically about how I use technology). If I keep the UserTesting tab open all day while I'm on my computer, I am usually able to be accepted for one test a day ($10), sometimes two. Don't expect to earn much more than this. It really adds up over time though and was a great nest egg for my Christmas gifts this year.