Widespread talk of the Semantic Grid seems to have cooled over the last couple of years. However, it is still under active development and moving along nicely. The formal effort began in 2001 as part of the e-Science program in the UK to reach a goal of semantic interoperability with an infrastructure
where all resources, including services, are adequately described in a form that is machine-processable….the Semantic Grid is an extension of the current Grid in which information and services are given well-defined meaning, better enabling computers and people to work in cooperation (from the Semantic Grid website).
Development seems to be gaining considerable speed as a greater number of research initiatives related to grid computing are underway. A good primer on the Semantic Grid effort can be found in this presentation (13 MB) given in Amsterdam in April by Dr. David De Roure, one of the lead researchers. Supercomputing Online also has a short piece about the effort.