Usually recruitment databases (Applicant Tracking Systems) provide XML, HTML or API interfaces for jobs and candidates data interchange.
JobMount job board have built-in interface for job or candidate profile posting via XML.
Candidate application can simply be emailed or application redirected to ATS interface/form.
might require custom integration for both job posting and candidate data sync.
some ATSes can only provide HTML jobs lists. This option would require a Job Spider to be activated for regular downloading, parsing and auto-posting of the jobs.