SwipeWell - The only tool dedicated to helping you save, organize, and reference marketing examples (so you never feel stumped).
Zero to Marketing - Short case studies that help you get better at marketing
AppGrowthLab (by SplitMetrics) - 55 app growth lessons from 30 app marketing experts
Miro Startup Program - $1000 to set up team collaboration
Kickstart Side Hustle Newsletter - Dwarf-size newsletter with viral marketing case studies
Marketing Examples - A gallery of real world marketing case studies. Updated every day.