Landing Pages by Viral Loops - Easily create a landing page for your referral campaign ✌️
Hunter TechLookup - Create lists of websites by technology for free
Best Referral Programs - A curated directory of startup referral programs
xZeitgeist - The most popular tweets categorized and ranked, every day
Rewardful - All-in-One Affiliate Management Software for SaaS
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!