Email Marketing: A Beginner's Guide - Master email marketing with these 3 short ebooks from Drip.
GrowthList - A crowd-sourced list of growth hacks
Google Sheets Email Marketing - Email automation and validations directly from Google Sheets
GrowthHackList - 100+ curated growth hacks for makers + early stage startups
HubSpot Free Email Marketing - Powerful drag and drop email marketing in the HubSpot CRM
Growth Hack World - Together We Rise