AngelList Jobs - See 1000s of startup jobs at the best startups. Get salary, equity and funding info upfront. Apply privately with one click. No recruiters, no spam. 20,000+ startups hiring.

Hunter TechLookup - Create lists of websites by technology for free

Glassdoor - Glassdoor is a jobs and career marketplace.

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!

Hired - Hired is the first two-sided marketplace created specifically for Engineers, Data Scientists...

WhatRuns - Extension that helps you identify technologies used on any website at the click of a button.