A few more here

Climate Change & Outreach Intern
Oxfam America
http://www.idealist.org/en/internship/130953-170
Washington, District of Columbia, United States

International Internship Program
Search for Common Ground
http://www.idealist.org/en/internship/130940-100
Washington, District of Columbia, United States

NCLB Internship
The Aspen Institute
http://www.idealist.org/en/internship/130936-230
Washington, District of Columbia, United States

Latin America and Caribbean Program Intern
Vital Voices Global Partnership
http://www.idealist.org/en/internship/130941-134
Washington, District of Columbia, United States

Internship: Global Programs Unit
Institute of International Education
http://www.idealist.org/en/internship/131038-328
Washington, D.C., District of Columbia, United States

Winter Intern Associate- Policy and Economics
The Public Forum Institute
http://www.idealist.org/en/internship/131033-161
Washington, District of Columbia, United States

Gifts and Stewardship Intern
United Nations Foundation
http://www.idealist.org/en/internship/131041-165
Washington, District of Columbia, United States