Spacedoo - Short actionable marketing hacks
Growth Hacker Marketing - Ryan Holiday's book, re-released and expanded
Your Growth Hacks Aren't Working - Free new book by Steli Efti on B2B customer acquisition
Primer - CSS toolkit and guidelines that power GitHub
Just a Line - Make simple drawings in AR, by Google
GrowthHackList - 100+ curated growth hacks for makers + early stage startups