Phil Agre has a background in AI and has moved into more social/political studies of the co-evolution of technologies and social patterns. He teaches in the information science school at UCLA. His course notes on the Semantic Web provide some introductory remarks and a collection of readings, most of which are on the web.
The main idea of the semantic web is machine-readable ontology standards. An "ontology" is a theory of the categories of things that comprise a given domain. Familiar examples of ontologies include taxonomies and controlled vocabularies. Every computer system uses an ontology. Computer systems that are built independently of one another, however, often cannot interoperate because they use different ontologies. Now that computer systems are heavily networked, numerous user groups have begun standardizing their ontologies. The semantic web consists of mechanisms for "marking up" ontologies and then processing them. [Information Retrieval Systems]