Hunter TechLookup - Create lists of websites by technology for free
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!
Top Lists - A leaderboard for Twitter lists
listshare - Create beautiful, interactive lists to share with the world.
Key Values - Find engineering teams that share your values
EmailMeTweets - Scheduled Twitter list notifications by email