Hi Greg, and Deb and Martha,
I have a major project going on that very topic. As Deb indicated, I've been using and adapting Personal Brain (http://www.thebrain.com) for doing exactly what you're describing, and in the course of that work have developed a fairly deep 'taxonomy' or 'pattern language' for identifying the people with whom we're connected, 'where they're anchored' (workplaces, learning places, community associations, etc.), and what capacities / assets they 'carry on board' (gifts, interests, skills, concrete resources, projects, values, etc.). Capacities / assets can also be attached to workplaces, associations, etc. - for example, a local Rotary Club might have a service project focused on youth in the community.
The taxonomy is incorporated in other work that I'm doing on building personal support circles (called the Star Raft), where we've embedded additional strategies for moving beyond 'mapping' in the direction of companionship, connection and contribution, finding the places in community where our capacities / assets are most clearly reflected - where our gifts would be understood and welcomed, moving from 'activity' to connection, and mobilizing the network.
I certainly share your interest in a mapping process that aids in identifying and visualizing this complex set of elements and relationship. Personal Brain is very close (it's a three-dimensional mapping system as opposed to a hierarchical system), but it's not 'there' yet in some important respects; unfortunately it can't be 'tweaked' to do everything we're thinking. At the moment, we're on the verge of an application development project with a graduate engineering course in a US university.