There isn't just one best job search site, though there are some really good ones. In fact, what's best for you, might not be a good site for someone else. Job searching is personal - you need to find job postings that are a match for your specifications and are located where you want to work.
That's why you need to spend some time checking out sites with job listings to see which ones give you the best results - that means quality job leads, not just a ton of them. A site full of jobs in New York, when you need to stay in Florida, for example, isn't going to be much help. Taking the time to target your job search upfront, will save time in the long run.
Given the job market, quality is much more important than quantity. Yes, you can send out hundreds of resumes, but my guess is that you're not going to get much of a response. Rather, it's better to spend less time applying to fewer jobs and more time writing customized cover letterrs and tweaking your resume so it's a match for the jobs you're applying to.
Use the job search engines to do some of the searching for you. A job search engine will search multiple sites for jobs based on the search terms you enter, including location and keyword. You'll be able to focus your search with just a few clicks of your mouse.
Also make sure that you check the niche sites which focus on jobs listed by career field and those that list jobs in specific geographic locations.
Do you have a favorite job site? If so, let us know what site has been working well for you.
Related: Top Job Search Engines | Top Part-Time Job Sites | Best Networking Sites | Job Listings
Are there websites where companies advertise openings direct without going thru the various job search sites?