I guess you should start by checking the websites of the relevant field you would like to perticipate.
this one offers you different options:
http://www.projects.aegee.org/takecontrol/index.php?id=12
also the NGO agency is a possiblity.
the amarican infornation about all kinds of fund raising are in
http://www.state.gov/g/drl/rls/50318.htm
and of course you know UNICEF
The The United Nations Children's Fund
