30 Seconds of Knowledge - Become a better developer, in every new tab.
The PM Interview - Practice PM Interview Questions (w/ timer).
Random User-Agent - Automatically change the user agent after specified period of time to a randomly selected one, thus...
Pramp for Product Managers - Practice product management mock interviews with other PMs
know/how Product Managers - A weekly newsletter with 5 practical tweet-length PM tips
Myskillwall - The best tool to prepare your job interview