A short history on the Palestine, Israel and Arab-Israeli conflict by The Middle East Research and Information Project (MERIP):
Palestine, Israel and the Arab-Israeli Conflict: A Primer

Comprehensive timeline of conflict:
Arab-Israeli Conflict Timeline

United Nations Office for the Coordination of Humanitarian Affairs:
Occupied Palestinian Territory

The Israeli Information Center for Human Rights in the Occupied Territories
B'tselem

Founded in 1993 by journalist John Wallach, Seeds of Peace is dedicated to empowering young leaders from regions of conflict with the leadership skills required to advance reconciliation and coexistence.
Seeds of Peace

The Electronic Intifada (EI) is a not-for-profit, independent publication committed to comprehensive public education on the question of Palestine, the Israeli-Palestinian conflict, and the economic, political, legal, and human dimensions of Israel's 40-year occupation of Palestinian territories. EI provides a needed supplement to mainstream commercial media representations of the Israeli-Palestinian conflict:

The Electronic Intifada

Truthdig is a great website devoted to “drilling beneath the headlines”. A simple search of “Palestine” will give you many wonderful articles. Chris Hedges has spent years covering the conflict and has many insightful articles found on the website:
Truthdig