The 2009 Top 100 US Job Site Niches report lists the 100 most searched for job categories. For each of these employment categories it lists the top ranked job boards according to Google but excludes the following:

* general-purpose job boards like monster.com
* subdomain spam from general-purpose job board sites like science.jobs.com (currently dominating the search results)
* sites exclusively powered by job search engines
* sites that are part of a large network of domains
* search engine spam made for AdSense (MFA)
* job sites that require job seekers to register or pay
* job guides and career book sites (many look deceptively like job boards)
* almost defunct boards and sites with only a handful of jobs
* job sites that don't publish dates on the job postings

Here is the executive summary - Looking at the major categories in this report that lack job boards is telling. Using my own personal definition of what a viable job board is and a bit of generosity, I'd estimate there may be just several hundred useful job boards in the US. Lots more are on the way and we will get to tens of thousands eventually -- but not today.

In order to compete with job search engines, niche job sites of the future will have to evolve. They will have to find new ways to provide value that cannot be usurped. Until that happens, you can expect to see the number of job sites with critical mass declining while the number of job pages associated with blogs, social networks and associations multiplying.

I know that lots of you have no use for job boards, but you may find it interesting to know if your own specialties are currently top 100... of course, that's job seeker demand, not employer demand.