Office of Personnel Management
The Office of Personnel Management (OPM) is an independent agency of the United States government, having responsibility for managing the civilian workforce.
OPM publishes the pay tables for the various pay scales (General Schedule, Wage Grade, etc.), handles the majority of insurance benefits and all retirement applications under FERS and CSRS, manages the majority of security clearances, and hires all Administrative Law Judges (though they are technically employees of the various agencies, OPM hires them to maintain the appearance of their neutrality).
The OPM director is an appointed office, appointed by the President and confirmed by the Senate.