Viking is a multi-user web-based collaborative management system for images and volumes which allows users to view multi-terabyte datasets, annotate images with their own annotation schema, and summarize the results. Viking was originally developed by James Anderson at the Marc lab for use with the first retinal connectome which was assembled using serial section Transmission Electron Microscopy and Computation Molecular Phenotyping.
To get an idea of how Viking works you can download a movie (2.5 minutes) which highlights current features.
A paper describing Viking and it's role in connectomics titled "The Viking viewer for connectomics: scalable multi-user annotation and summarization of large volume data sets" was published in the Journal of Microscopy. It provides a good overview of architecture and philosophy along with some preliminary results.
Viking's role begins after images are collected and registered into a volume. If you are looking for the Scientific Computing Institute's automatic image registration tools used to build the first retinal connectome you should start here.
A rendering of all the tracing as of 7/20/12 is available here.