The following link will take you to the Office of Personnel Management (OPM) web page for vacancy announcements in federal law enforcement and DoD. If you are interested in intelligence vacancies, type in the occupational series 0132, and complete the rest of the query. Please be aware that these vacancies, which are usually open only for a two week period, are for U.S. citizens only

http://jobsearch.usajobs.opm.gov/series_search.asp