See my thread about reapplying to jobs
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=362x193.There have been a few positions on state job boards though in which I believe there really was a job because I was contacted and interviewed. In some of these circumstances, they seem to have relatively high turn over. In one of these cases, it makes me wonder why they don't want to hire me when I really want to work there (although maybe there is a reason that I don't, 10 positions and 3-4 openings every year, hmmm...). Other comapnies seem to be ridiculously picky. In one case, I was contacted two months after applying to a posted position for which I met every single requirement. I went for the interview. Even before the interview started, the interviewer told me that myself and another qualified candidate would be interviewed that week but they were looking for more candidates. After I interviewed, the position was posted again. I contacted them a month later and they said that I was still in the running but they were still considering other candidates. A few weeks later, I received a rejection notice.
As for other jobs, they may or may not have jobs availible at the moment. I think some large firms build an applicant pool for positions they might need in the future. You might not be contacted because you are actually competing against college recruited candidates and networked candidates too, not just the ones who responded to the website as these positions open up.