Ask HN: Good strategies for finding jobs with companies in specific fields?

There are plenty of job/contract-search websites focused on location (or lack thereof), or tech. What are some good strategies for finding jobs in any location, or using any tech, but in specific fields?

For example, I have deep passions for travel and aviation, as well as enduring interests in embedded software and telephony. I've typically found that I perform much better in roles that engage at least one of my passions/interests. What are some good strategies for searching for jobs in certain "verticals", i.e. companies involved in specific fields?