UserTesting.com - Usability testing has never been easier. Get videos of real people speaking their thoughts as they use websites, mobile apps, prototypes and more!
Cohort - Find the people you need through the people you already know
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
A Guide to Marketplaces - Everything you need to know about building a marketplace
Userbrain - Easy, fast, and affordable user testing for websites and prototypes.
Cadre - Cadre is a technical staffing agency and recruiting firm.