Careerage is best for resume database
Will - MightyRecruiter is a good place to start. You can post to a ton of free job boards (including LinkedIn), and paid ones if you want more visibility. They also have a resume database where you can search millions of resumes, and a service called JobPromote with which you can get a job advertising plan that's custom to you. I would check out the free trial and see what you think.
I use applicant tracking system - SignalHire, that accumulates 200M resume database from different public networks, such as LinkedIn, Stack Overflow, GitHub, Facebook, etc. This system very useful for me.
I regularly use Resumerobin.com - it's fast and better quality than Indeed
Well, I use Intelifi. It's a reliable source for background checks, you can check out their services at http://www.intelifi.com/services/