Determining when a given person will be receptive to solicitations to leave his or her current employer is like trying to time the stock market. Maintain a list of links to these on your site, but some great information also comes from newsletters not specifically tied to recruiting. Applicants can send you a resume in a second via mouse-click. An autoresponder sends an automated template message to the job seeker even before you have a chance to open the e-mail. You may be entitled to have your jobs listed there free, as well as have access to resumes.
Most companies have no brand recognition with job seekers, especially relocating ones.
Some of the fee-based Internet career services are worth the money. But which ones are best vary, based on the employer's industry, location, job title, and even time of year.