VolunteerMatch is a nonprofit organization with a mission to help everyone find a great place to volunteer, and offers a variety of online services to support a community of nonprofit, volunteer and business leaders committed to civic engagement.
Although focused to presential volunteering, they’ve got a virtual volunteering section with lots of opportunities.
The categories are not very clear and are more related to the NGO field of action than to the profile of the volunteer needed (i.e. a fundraiser under “Animals” section – maybe not that wrong ;) Thus, volunteering opportunities should, at least, be browsed by profile required and/or NGO field of action. Say: I am a fundraiser and want to work with someone in the field of whales protection.
By the way, there’s more than 5,000 opportunities today only for the virtual volunteers section, wow! :)