I would compute the value of a given volunteer's time on hte basis of whatever
they make elsewhere.  If they don't work elsewhere, I would use the value of
the type of work they are doing on the local market.  If all else fails, I
would make up some plausible number agreeable to the volunteer.  In any case, I
would make sure she certifies both the time expended and its value on his/her
time and effort sheets or some other auditable documentation.

Bill Campbell
Director, Grants & Research
University of Wisconsin-River Falls