Here's a long list of job-posting sites organized by field of interest: http://faculty.ccbcmd.edu/~hzlotow1/Top_100_Niche_Job_Sites.pdf from members of the LinkedIn group Mid-Atlantic Career Counseling Association.
Keeping in mind that by the time a job is posted to a site such as one of these listed, it has already been promoted to people in the company or organization and thereby word of mouth. Lesson here: network (communicate with people you know; use social networking sites, such as LinkedIn*) to get ahead of other job seekers to take advantage of that fact. At the same time, use the job lists for applying to specific jobs as well as for ideas about what will appeal to you and what you might have skills for and want to develop.
*new to me: http://www.facebook.com/socialjobs
