Farnam Street – Shane Parish – Mental model and how to make decisions.
Paul Graham – Founder of Y Combinator – Great articles on startups and new products.
Ben Horowitz – Half of Andreessen Horowiz – Hard things about startups and management.
Breaking Smart – Online blog book – How software is eating the wold.
Andrew Chen – Growth Hacking – How to build growth into your product.
XKCD – Web Comic
PolyMth - Product Leadership 