Content Marketing Stack - A curated directory of content marketing resources
Q-Stats - Get free marketing insights for every question on Quora.
This Won't Scale by Drift - 40 free marketing playbooks to help you grow your business
Site Rank Data - View historical rank information of websites via time series charts.
GrowthHackingIdea.com - One short, curated growth hacking idea a day to your email
HypeStat - HypeStat is free statistics and analytics service, where you can find information about every website.