Official Federal Republic of Nigeria site

The Presidency

Hon. Speaker of House of Representatives

Nigerian Navy

Nigerian Army

Nigerian Police

Nigerian Customs Services

Bureau of Public Enterprises

Central Bank of Nigeria

Corporate Affairs Commission (CAC)

Department of Petroleum Resources

Federal Ministries of Commerce

Federal Ministry of Science and Technology

Independent National Electoral Commission(INEC)

Joint Admissions and Matriculation Board

Nigerian Communications Commission (NCC)

Nigerian Mining Corporation

Nigerian Investment Promotion Commission(NIPC)

National information Technology Development Agency

Nigerian Ports Authority (NPA)

National Export Processing zone Authority (NEPZA)

Nigerian Tourism Board

National Orientation and Public Affairs

Nigerian Stock Exchange (NSE)

National Council on Privatization

National Broadcasting Commission

National Centre for Economics Management & Administsration

Nigerian LNG Limited (NLNG)

Nigerian Oil and Gas Industry

National Hospital

National Space Research & Dev. Agency

Nigerian Postal Service(NIPOST)

Nigerian National Petroleum Corp.(NNPC)

Nigeria Oil and Gas Industry Online

Nigeria Investment Promotion Comm.(NIPC)

Nigerian Tourism Development

Niger Delta Dev. Commission

Nigerian LNG Limited(NLNG)

Nigerian Institute for Social & Econ. Research

Petroleum Equalisation Fund

Voice of Nigeria

All links not verified though,Let me know if you have any addition or broken link