Peacekeeping has been used to describe a number of activities including nonviolent intervention in conflict, bearing witness to conflict, or passive resistance to violents or threats of it. More recently the term is frequently related to official United Nations peacekeeping operations.
AllAfrica Peacekeeping - site that aggregates and distributes news from more than 130 African news organizations for reports on Peacekeeping activities on the continent.
Australian Peace Operations Training Centre - focuses on operations of the Australiaqn Defence Forces in global peacekeeping operations.
Global Policy Forum - maintains a useful website to UN related efforts, both past and present as well as links to articles and other information sources on the topic.
SIPRI Multilateral Peace Operations - a searchable database of operations involving more than one country from the Stockholm International Peace Research Institute.
UN Dag Hammarskjold Library - Documentation Center for official documents related to UN Peacekeeping Operations
United Nations Institute for Training and Research (UNITAR) - peacekeeping training resources used for training peacekeepers from around the globe.
United Nations Peacekeeping - the official UN Department of Peacekeeping Operations (DPKO) web site that gives current and historical information on operations, finance, and other elements of the peacekeeping work. Currently (December 2012) THERE ARE 16 ACTIVE un Peacekeeping missions.
Wikipedia's Peacekeeping page - good overview beyond UN peacekeeping operations as well as links to some useful articles and critiques of peacekeeping efforts.