The UNV Online Volunteering service connects volunteers with organizations working for sustainable human development. Volunteers contribute their skills online to help organizations address development challenges.
Organizations collaborate with online volunteers over the Internet to strengthen the impact of their development work.
http://www.onlinevolunteering.org/en/index.html
Other volunteer pages (Finding volunteers and managing them):
http://www.worldvolunteerweb.org/resources/how-to-guides.html