If you are wanting to leverage a third party job board, I suggest you look at http://blog.jobamatic.com/2010/02/setting-up-contextual-widgets.html. If you are wanting to have your own job board, leveraging an open source job board (there are plenty looking at the results of https://www.google.com/search?q=open+source+job+board and http://www.jobboarddoctor.com/resources/job-board-software/) that include widgets or let you build your own is fairly straight forward.