Content Marketing Stack - A curated directory of content marketing resources
Feather Attribution - A free and tiny javascript library to track UTM tags, ref and referrer data client side so you can store these in your own database.
This Won't Scale by Drift - 40 free marketing playbooks to help you grow your business
LoyalAs - Get and track referrals automatically.
GrowthHackingIdea.com - One short, curated growth hacking idea a day to your email
ToneDen Lasso - Put fan and customer acquisition on autopilot