O'Reilly's XML classic.

Opera has several browser plugins and lively projects to build support for the Semantic Web.

One of most interesting plugins is the Tabulator RDF Browser Plugin. It's one of the few RDF tools that actually works.

The Tabulator Developers Notes ( and source code ) at MIT's DIG-CSAIL.

Updated Oct 20 2008: new link

A really excellent example of what can be accomplished with a pragmatic approach to implementing RDF and Semantic Web applications, by Drs. Marwan Sabbouh and Joseph K. DeRosa at the Mitre Corporation. They use OWL ontologies to map between databases in three basic steps:

1. Express any software component’s formalism as an ontology,
2. Map the component’s ontology to the domain ontology, and thus
3. Integrate components at the semantic level without writing integration code.

Updated Sept 17 2008: new links

One of the great contributions to the world of business rules in the last decade is the OMG Model Driven Architecture for Business Rules. The OMG link will take you to a page listing several formats for the article. I suggest using the PDF format for Business Semantics of Business Rules, it's about 240K. They also have MS Word and RTF formats.