I dont know Your situation nor location but why you dont host local meetup groups and let the group know that you are hiring?

What makes you think you have different requirements?

I think there are regional differences to be accounted for. NY VS SF Bay may actually be more similar then, say somewhere in alabama or ohio. And I suspect things are very different in the UK, though probably not as much as in eastern europe, south america, or asia.

So I think you should quantify your question. Otherwise expect a fair bit of bias based on the locality of the commenter.

LinkedIn is very resourceful for both Recruiting and Job Searching. Doesn't matter if you're looking for big or small their database is large enough to find niche markets for both the employee and employer.

Linkedin seems popular for small companies. What is your location?

Indeed has given me some good engineers and you can also try writing and sharing a post on LI/ adding pics helps!

Reddit! :D a gigantic number are technically savvy

Where specifically?