Depict.ai - Amazon-quality product recommendations for any online store
Setalist - The easiest way to make awesome lists for the internet
Suto - Get one-on-one expert product recommendations.
Hunter TechLookup - Create lists of websites by technology for free
MailChimp Product Recommendations - Easily build automated personalized email marketing
Techmap.io - Techmap is a workplace search engine to find companies using technologies (e.g., Rails, PHP, Java, etc.) that are used internally. Finally, a "Google for Workplaces" that helps people find a place to work with technologies they love!