My own search has been on LinkedIn, as well as sites like Otta. The key for me to get more callbacks has been to personalize my resume for each job description (I even made a tool to do it for me [0]) and then to follow up with the hiring managers for the job.
Out of the stacks of resumes that get submitted to the black hole, it really does feel like a grind, but the little bit extra by reaching out to the recruiters/hiring managers seems to make the boost to at least get to the first round screen.