My thought is that requiring potential volunteers to email me will filter out those least likely to actually do something. Also, I want to be able to coordinate who is working on what so that uselessly duplicate work isn't being done.
Can't you filter the volunteers by first posting the list, then requiring that the people who want to work on any of the things mentioned e-mail you? My intuition would be that your current method filters out a disproportionate amount of people who would actually do things.
Those who wish to volunteer some of their time toward reducing existential risk and increasing our chances of a positive singularity can follow the directions on SingularityVolunteers.org.
And as a freshly hired Singularity Institute researcher, I also have my own list of tasks that, if completed by volunteers instead of myself, will speed along the delivery of the projects I'm working on: an 'FAI Open Problems' document, two papers bound for peer review, metaethics research, and more.
So if you'd like to help me out with any of my volunteer-doable tasks, please contact me: luke [at] singinst [dot] org.
Thanks!