Google Open Source - All of Googles open source projects under a single umbrella
Ubersuggest - Want more traffic? Ubersuggest shows you how to win the game of SEO. Just type in a domain or a keyword to get started.
LaunchKit - Open Source - A popular suite of developer tools, now 100% open source.
Keyword Explorer by Moz - Find the best keywords to improve your website's SEO traffic
Open Source @IFTTT - A collection of IFTTT OSS projects.
Content Marketing Stack - A curated directory of content marketing resources