Can anyone tell me which federal agencies hire entry-level 1811's through means other than USAjobs.gov?

It seems that the majority of federal jobs can now be found on the OPM website, but I know that ICE, for example, hires entry-level criminal investigators through its own recruiters, and uses USAjobs to fill other positions (as opposed to, say, the FBI, which seems to be moving towards integration with USAjobs). What other agencies, if any, do this? What about other law enforcement positions? And lastly, where are the best sites to find job vacancies in state, county, and/or municipal law enforcement? Thanks!