All the popular blogs are trying to leverage job boards to make some extra income. See some of the examples (Guy Kawasaki, ReadWriteWeb, Problogger) and you will know how bloggers make use of such avenue to earn their incomes.
Needless to say that in order to create an active and profitable job board you need first to have a blog focused on a specific niche, and decent amount traffic.
The advantage of this method is that it is passive. Once you have the structure in place, the job listings will come naturally, and you can charge anywhere from $10 up to $100 for each.

I have managed to find a list of popular job board software below:

1. JobThread

JobThread connects employers with the most qualified candidates

2. Web Scribe Job Board

WebJobs lets you run a job board on your web site. Their incredible features allow you to easily compete as a general job board, or the flexibility to run a niche site. It’s used by thousands of corporations, universities, recruiters, and webmasters to power their job board.

3. SimplyHired Job-o-matic

Simply Hired’s publisher program makes it easy to add relevant job listings to your website. Our job advertising network offers web publishers the ability to add valuable content to their site and get paid whenever a visitor clicks a sponsored job.

4. Jobbex

Jobbex Job Board Software let’s you launch an easy-to-use advanced Job Board while providing all the key features to generate revenue and be successful in a competitive job board market. Jobbex is scalable and a fully customizable solution to meet your unique Job Board requirements.

Hope it helps.
Cheers!
Patrick