99tests offers a variety of testing opportunities that can make you money, including software and apps. You’ll be specifically looking for bugs as you use the app and keeping a log of everything you find. Your pay depends on the complexity of the task and the estimated length of it. Some developers want a more in-depth log file, which will take you longer and pay more. You’ll get your payment via PayPal once your task is completed and approved by 99tests and the developer. Be sure to fill out your profile completely, as developers will find you in the system by matching your demographics to their need for testers.
The site also features app testing contests that you can win some extra money for participating in!