Govt.
Government

UN
United Nations

NGO
Non-Governmental Organization

USAID
United States Agency for International Development

EPA
Environmental Protection Agency

FBI
Federal Bureau of Investigation

IRS
Internal Revenue Service

CIA
Central Intelligence Agency

NATO
North Atlantic Treaty Organization

EU
European Union

WHO
World Health Organization

IMF
International Monetary Fund

WTO
World Trade Organization

FAO
Food and Agriculture Organization

UNESCO
United Nations Educational, Scientific and Cultural Organization

ASEAN
Association of Southeast Asian Nations

NDA
Non-Disclosure Agreement (sometimes used in government contexts)

NAFTA
North American Free Trade Agreement

DOJ
Department of Justice

HUD
Department of Housing and Urban Development