30 Seconds of Knowledge - Become a better developer, in every new tab.
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!
Random User-Agent - Automatically change the user agent after specified period of time to a randomly selected one, thus...
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
know/how Product Managers - A weekly newsletter with 5 practical tweet-length PM tips
Userbrain - Easy, fast, and affordable user testing for websites and prototypes.