If 80% of the job openings out there are never advertised on any of the websites, listings or career fairs you might have access to -- how the heck do you find them? Clearly, somebody is finding them; if they hadn't been found, they would have been advertised!
Here's a great article that describe strategies you can use to find the hidden jobs. Many of them involve people and networking--keeping your ears open, stating your purpose to folks you come in contact with, joining a LinkedIn group.
A few you might not have thought of: set up a Google news alert. I've used these alerts for some time; you do have to pick and choose your keywords carefully, but you can get up-to-the-minute information on companies and their new initiatives that are likely to need new employees.
And: try contacting a prospective employer directly. Clearly this isn't going to work if you have your eye on a mom & pop operation--a company with all of three employees, two of whom are the offspring of the CEO. But if you have your sights on a few companies with 50+ employees or so, then (a) it's likely there will be turnover in the ranks within the next few years (and you know that's how long job-searches take these days); and (b) small companies are likely to be entrepreneurial, up-and-coming, and looking for a go-getter like you to boost profits and efficiency!
(Thanks and a tip o' the hat to Joyce Tesar for forwarding me this article!)