Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Flockjay - $0-upfront tech sales academy to break into tech 💪
Curious - 15,000 lessons in tech, biz, DIY and more. Grow your skills.
Angle 2 Mockups - A giant Sketch Library for creating app presentations
Indie Hackers - Connect with fellow entrepreneurs, developers, and bootstrappers who are sharing the strategies and revenue numbers behind their companies.
SketchCasts - A weekly screencast, all about how to use Sketch