According to its financial statements posted, the biggest funder of Ma'an would appear to be DfID – ie. the UK government. Next is Search for common ground, which in turn declares is funding to be: http://www.sfcg.org/sfcg/sfcg_funders.html
Foundations and Non-Profit Organizations·
Amnesty International· Brodsky Family Foundation· Carleton University· Chasdrew Fund· Coexist Foundation· Educational Development Center· Foundation for Global Community· Gill Foundation· Haas Fund· International Alert· International Medical Corps· Johnson Family Foundation· Kathmandu University· Kellogg Foundation· Marble Collegiate Church· MacArthur Foundation· National Endowment for Democracy· New Field Foundation· Nuclear Threat Initiative· Overbrook Foundation· Rational Games· Rockefeller Brothers Fund· Rockwool Foundation· Stockholm International Peace Research Institute (SIPRI)· Skoll Foundation· Alan B. Slifka Foundation· Cal Turner Family Foundation· University College London· US Institute of Peace
Businesses· Barrick Gold· Berry Moorman· Chevron· Hunton & Williams, Attorneys at Law
Governments· Australian Agency for International Development· Belgian Ministry of Foreign Affairs, Foreign Trade and Development Aid· Canadian Foreign Affairs· Canadian International Development Agency (CIDA)· Danish Ministry of Foreign Affairs· Finnish Ministry of Foreign Affairs· French Ministry of Foreign Affairs· Netherlands Ministry of Foreign Affairs· Norwegian Foreign Ministry· Swedish International Development Agency (SIDA)· UK Foreign and Commonwealth Office (FCO)· UK Department for International Development (DFID)· US Agency for International Development (USAID)· US Department of State
Multilateral Organizations· European Union· United Nations Children's Fund (UNICEF)· United Nations Democracy Fund (UNDEF)· United Nations Development Fund for Women (UNIFEM)· United Nations High Commission for Refugees (UNHCR)· World Bank
Plus a small amount from one of the ubiquitous UN departments for supporting the Palestinians The number of ways the Palestinians get money from governments, international organizations, etc. etc. never ceases to amaze.