Are nuclear weapons and materials being secured and destroyed?

There are several agencies engaged in this work. Here are a few:

1) The International Atomic Energy Agency is tasked with oversight of nuclear and related facilities in 140 signatory states. They receive reports from the countries involved and engage in a program of regular inspections. For information on their activities, go to: http://www.iaea.org

2) The G8 meeting in Canada resulted in the creation of the G8 Global Partnership Program. The Foreign Affairs Canada website advises:
The Global Partnership is intended to address one of the most serious security threats facing our world today by preventing terrorist groups from obtaining weapons and materials of mass destruction (WMD) to carry out their campaigns.

In recognition of this threat, G8 Leaders, under the guidance of Prime Minister Jean Chrétien (1993-2003), committed the G8 to a program aimed at preventing the acquisition of weapons and materials of mass destruction by terrorists or those who shelter them. At the Kananaskis Summit, G8 Leaders, from the United States, United Kingdom, France, Germany, Italy, Japan, Russia, the European Union and Canada, united to launch the G8 Global Partnership Against the Spread of Weapons and Materials of Mass Destruction <http://www.g8.gc.ca/2002Kananaskis/kananaskis/globpart-en.asp> . The eight countries agreed to raise up to US $20 billion to support cooperation projects, initially in Russia. As Chair of the G8 for 2002, Canada reinforced its leadership on the initiative by committing up to CDN $1 billion over 10 years, beginning in 2003.
For further information on their priorities and progress go to: http://www.dfait-maeci.gc.ca/foreign_policy/global_partnership/menu-en.asp

3) Senators Nunn and Lugar in the US founded NUNN-LUGAR COOPERATIVE THREAT REDUCTION PROGRAM.
The goal of NUNN-LUGAR is to lessen the threat posed by weapons of mass destruction, to deactivate and to destroy these weapons, and to help the scientists formerly engaged in production of such weapons start working for peace.
For updates on progress, go to http://nunn-lugar.com or http://lugar.senate.gov/nunnlugar.html

4) The Nuclear Threat Initiative (NTI) was founded in January 2001 by Mr. Ted Turner of Turner Broadcasting and Senator Nunn. NTI's mission is to strengthen global security by reducing the risk of use and preventing the spread of nuclear, biological and chemical weapons. NTI seeks to raise public awareness, serve as a catalyst for new thinking and take direct action to reduce these threats. For their 2004 Report go to: http://www.nti.org/e_research/cnwm/overview/2004report.asp