When I first started looking for jobs, my brother the engineer told me to find a relevant staffing agency. I tried to explain that in science, you have to get a job by knowing who to talk to at a meeting and having impeccable timing for their grants. He was slightly baffled, "What if you don't want to work for someone you already know? What if you want to change fields, or work in industry?" I didn't know, but as baffling as I was finding the entire search I was pretty sure Scientists don't use Staffers.
Actually, this is totally false. I've now met a couple scientists who've been hired through staffing/recruiting agencies, and I've been interacting with these recruiters more myself. In my limited experience, this is a better place to find an industry job than an academic position, since many of these jobs come from mid-size to multinational companies that have contracted the hiring component of their HR to another company. Even though I haven't scored so much as an interview from any of my interactions with recruiters, I really like interacting with them. They are always looking for new and hire-able people (as a recruiting agency, having new capable people to hire is their product). These a predominantly the people/companies I am following on Twitter.
Some places will call you after you've submitted your resume to their site, and this gives you a good chance to talk about what you can expect from them and from a job. They always ask what salary you are willing to accept (I don't fill this out online because I am waiting to talk with a recruiter), and so I ask what is typical for their area and the jobs I might qualify for. Examples- associate researcher (Ph.D. with no experience) in Colorado was $45-50K, in San Diego $65-80 and in Boston $80-95. All of these places encourage you to stay in touch (again, you are the product that they have to offer), and mention when you see jobs they can put you up for. And from the scientists I know who've been placed this way, this is really the key- stay in touch!
This is really the ultimate test of your resume and coverletter, someone who doesn't know any more about the job than the blurb posted online is going to fit the resume you submit to that discription- it helps me to keep that in mind. Am I presenting myself as a match for the position, and not just a generally smart person? Yes, this whole process takes a lot of your time, but in principle, but being presented by the recruiter who has a long standing relationship with the company looking to hire gives you more credibility.
Oh, one more thought, many of these jobs are presented as "temp" or short term contract jobs. That's not the whole story, for most of these posted positions, if you are successful in the position, a permanent or full time position will follow. So don't take those temp postings too lightly! Staffers know the field and can help you gauge your marketability, which makes them a pretty unique resource.
At the very least, I like getting called after I drop my resume/CV into the internet black hole, it's like someone is actually recieving it.