The Global Peace Index (GPI)--founded by Steve Killelea--is a measure that governments can use to help increase the peacefulness of their nations. Nations hold the key to peace and can improve their nation's peacefulness by supporting initiatives at national and local levels and by using the GPI to measure the success of their initiatives.
The index is composed of 24 qualitative and quantitative indicators from highly respected sources, which combine internal and external factors ranging from a nation's level of military expenditure to its relations with neighboring countries and the level of respect for human rights. These indicators were selected by an international panel of academics, business people, philanthropists and peace institutions. The GPI is collated and calculated by the Economist Intelligence Unit.
The Global Peace Index (GPI) shown on Steve Killelea's Vision of Humanity website shows rankings for 140 countries analyzed in 2008 and 121 countries analyzed in 2007, as well as year-on-year comparison. You can see the rankings here.
You can see a world map of the GPI here.