From: http://www.awm.gov.au/encyclopedia/korea_unlist.htm:
Twenty including:
Korea: United Nations Force Contributions
A listing of countries and level of contribution:
Australia: Two infantry battalions, part of the 1st Commonwealth Division; two destroyers or frigates; one aircraft carrier and a fighter squadron.
Belgium: One infantry battalion.
Canada: One reinforced infantry brigade, including tank and artillery forces, part of the 1st Commonwealth Division; three destroyers; and a squadron of transport aircraft.
Colombia: One infantry battalion and a frigate
Ethiopia: One infantry battalion.
France: One reinforced infantry battalion.
Greece: One infantry battalion andd transport aircraft.
Luxembourg: One infantry platoon.
Netherlands: One infantry battalion and naval forces.
New Zealand: One regiment of artillery, part of the 1st Commonwealth Division
Thailand: One infantry battalion; naval forces; air and naval transports
Turkey: One infantry brigade.
Union of South Africa: One fighter squadron.
United Kingdom: Two infantry brigades, one armoured regiment, one and a half artillery regiments, one and a half engineer regiments and supporting ground forces, all part of the 1st Commonwealth Division; British Far East Fleet; and Sunderland aircraft of the RAF.
United States of America: The Eighth Army, of six army divisions and one Marine division; Naval Forces Far East (three task forces); and Far East Air Forces (three air forces).
Denmark, Italy, India, Norway and Sweden contributed medical units.