Below is a collection of useful data sets regarding political violence and terrorism.
Causes
[Macro Data] Fearon, James and David Laitin. "Ethnicity, Insurgency, and Civil War," American Political Science Review 97 (1): 75-90. (www.stanford.edu/group/ethnic/publicdata/publicdata.html)
[Macro Data] Collier, Paul and Anke Hoeffler. "Greed and Grievance in Civil War," Oxford Economic Papers 56: 663-695. (http://users.ox.ac.uk/~ball0144/research.htm)
Recruitment
Israel / Palestine: Kruger, Alan and Jitka Maleckova. "Education, Poverty, and Terrorism: Is There a Causal Connection?" Journal of Economic Perspectives 17 (4): 119–144. (www.krueger.princeton.edu/terrorism2.pdf)
Mexico [Not yet available]: Trejo, Guillermo. "Insurgency, Democracy and Repression: The Logic of Preventive Rebellion in Chiapas, Mexico" and "Redefining the Territorial Bases of Power: Peasants, Indians and Guerrilla Warfare in Chiapas, Mexico." (http://unesdoc.unesco.org/images/0013/001387/138777E.pdf)
Organization
[Macro Data] Sambanis, Nicholas. "Do Ethnic and Non-Ethnic Wars Have the Same Causes? A Theoretical and Empirical Inquiry (Part I)," Journal of Conflict Resolution 45 (3): 259–82.
Multiple Regions PRIO/Uppsala Conflict Armed Conflict Dataset (www.prio.no/cwp/ArmedConflict/)
Multiple Regions Minorities at Risk Data (www.cidcm.umd.edu/inscr/mar/)
Multiple Regions MIPT Terrorism Knowledge Database (www.tkb.org/Home.jsp)
Multiple Regions State Failure Task Force (www.cidcm.umd.edu/project.asp?id=19)
Violence
Global Lacina Dataset on Battle Deaths (www.prio.no/page/CSCW_research_detail/Programme_detail_CSCW/9649/45656.html)
India: Varshney Ashutosh and Steven Wilkinson. Varshney-Wilkinson Dataset on Hindu-Muslim Violence in India, 1950–1995, Version 2. (http://webapp.icpsr.umich.edu/cocoon/ICPSR-STUDY/04342.xml)
Greece: Kalyvas, Stathis. 2000. The Logic of Violence in Civil War. New York: Cambridge University Press.
Vietnam: Kalyvas, Stathis and Matthew Kocher. "Dynamics of Violence in Civil War: Evidence from Vietnam." (www.people.umass.edu/woojin/ConferencePapers/Kalyvas&Kocher.pdf)
Nepal: Murshed, S. Mansoob and Scott Gates. "Spatial-Horizontal Inequality and the Maoist Insurgency in Nepal," Review of Development Economics 9 (1): 121–134.
Congo: Roberts, Les. Eastern DRC Mortality Survey. (www.theirc.org/mortality/). {2006- IRC redesigned website; see resources list at www.theirc.org/resources/documents.html}
Colombia: Rubio, Mauricio. "Kidnapping and Armed Conflict in Colombia." (www.prio.no/cscw/pdf/micro/techniqes/Kidnapping%20and%20armed%20conflict%20in%20Columbia.pdf)
Colombia: Restrepo, Jorge, Michael Spagat, and Juan Vargas. "The Dynamics of the Colombian Civil Conflict: A New Dataset." (http://personal.rhul.ac.uk/pkte/126/Documents/Docs/Database%20civil%20war.pdf)
Northern Ireland: Sutton, Malcolm. Index of Deaths in Northern Ireland. (http://cain.ulst.ac.uk/sutton/)
Iraq: Data from www.iraqbodycount.org is used in this intriguing paper by Johnson, Spigat, et al. "From Old Wars to New Wars and Global Terrorism." http://personal.rhul.ac.uk/uhte/014/PaperLANL6.pdf
Termination
Multiple Regions Data on Peace Agreements. (www.incore.ulst.ac.uk/services/cds/agreements/)
[Macro Data] Doyle, Michael and Nicholas Sambanis. "International Peacebuilding: A Theoretical and Quantitative Analysis," American Political Science Review (December 2000): 779–802. (www.worldbank.org/research/conflict/papers/peacebuilding/)
[Macro Data] Hartzell, Caroline and Matthew Hoddie. "Institutionalizing Peace: Power Sharing and Post-Civil War Conflict Management," American Journal of Political Science 47 (April 2003): 318–332. (www-polisci.tamu.edu/faculty/hoddie/)
[Macro Data] Regan, Patrick. Data on Third-Party Intervention and Civil War Termination. (http://bingweb.binghamton.edu/~pregan/)
[Macro] Sambanis, Nicholas. "Partition as a Solution to Ethnic War: An Empirical Critique of the Theoretical Literature," World Politics 52: 437-483. (www.worldbank.org/research/conflict/papers/partition.htm)
Multiple Regions Other Data on Truth and Reconciliation Commissions: (www.incore.ulst.ac.uk/services/cds/themes/truth05.html).
Sierra Leone: Statistical Appendix to the Report of the Truth and Reconciliation Commission, Sierra Leone (www.hrdag.org/resources/publications/SL-TRC-statistics-chapter-final.pdf). ]
Colombia: Deininger, Klaus et.al. "Towards Sustainable Return Policies for the Displaced Population: Why are Some Households More Willing to Return than Others?" (www.hicn.org/papers/wp07.pdf)
Human Rights/State Repression
Cingranelli-Richards (CIRI) Human Rights Project Dataset, a set of standards-based quantitative information on government respect for 13 internationally recognized human rights for 195 countries, annually from 1981–2004. It is designed for use by scholars and students who seek to test theories about the causes and consequences of human rights violations, as well as policy makers and analysts who seek to estimate the human rights effects of a wide variety of institutional changes and public policies including democratization, economic aid, military aid, structural adjustment, and humanitarian intervention. (www.humanrightsdata.org)
The Political Terror Scale (2006): Since the early 1980s, a group of human rights scholars and students at Purdue University have produced The Political Terror Scale, in which countries are coded on a scale of 1–5 according to their level of terror in a previous year. Description by Mark Gibney and Matthew Dalton (.pdf). The Political Terror Scale dataset (.xls).
Multiple Regions: Ball, Patrick. Human Rights Data Analysis Group. (http://shr.aaas.org/hrdag/) and (www.hrdag.org/about/projects.shtml)
Rwanda: Davenport, Christian. GenoDynamics: Understanding Genocide Through Time and Space. (www.bsos.umd.edu/gvpt/davenport/genodynamics/data.htm)