Fiverr - One marketplace, millions of professional services.
Amazon Mechanical Turk - The online market place for work.
HireOwl - Hiring students for internships and freelance projects
SerpClix - SerpClix is a click exchange network used to send more real clicks to your Google SERP. You can click to earn money or buy clicks to rank higher on Google.
Upwork - Forget the old rules. You can have the best people. Right now. Right here.
Testable Minds - Testable Minds is the platform used by researchers from the world's leading universities to recruit participants for their psychological and behavioral experiments.