Depict.ai - Amazon-quality product recommendations for any online store
Hunter TechLookup - Create lists of websites by technology for free
Operator - Looking for something? Make a request and we'll find it.
xZeitgeist - The most popular tweets categorized and ranked, every day
Rex - Rex is a real estate software platform.
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!