What amazing web services are available, free of charge, for volunteers to use in their volunteer organizations?

Someone told me about an amazing mapping application from ESRI, free for use by volunteer-based applications. Otherwise, this ESRI application is a very expensive product. This lead me to wonder what else was available, under similar terms, that could be used to benifit volunteer organizaitons.

Through my volunteering, I participate and am active in these activities that could all potentially benefit:
--- Scout leader in Cub Scouts
--- Active on Disaster Action Team, Red Cross
--- Alumni Board for VCU (Virginia Commonwealth University)
--- lots of other ad hoc activities during the year