Amazon Mechanical Turk - The online market place for work.
Micro Work 4 all - New Website aiming to get more workers and job seekers to perform tiny task and make money.
Universal Data Tool - Machine learning, data labeling tool, computer vision, annotate-images, classification, dataset
Picoworkers - Earn money from doing short, easy tasks similar to Microworkers. Picoworkers is the best alternative to Microworkers I ever find.
Labelbox - Build computer vision products for the real world
Fiverr - One marketplace, millions of professional services.