The problem with a lot of the job sites is that employers list openings that they full intend to fill from within, but are compelled to look outside the company. However, I would certainly give them a try.

My daughter had great success with careerbuilder.com. When all of her friends were telling her how hard it was to find a job, she spent an hour per day for less than a week sending in her resume and/or application, and she had 10 interviews and even more calls for jobs that ultimately didn't interest her. She got 3 solid job offers from there.