Jena ARQ
Jena Fuseki
W3C RDF/XML validator, which can generate graph images of data
Rhizomik RDF to SVG form for generating graph images of data, from the GRIHO research group
SPIN (SPARQL Inferencing Notation) home page and W3C submission
RDF Schemarama test; see also the Dan Brickley blog posting CheckRDFSyntax and Schemarama Revisited
SPARQLWrapper Python library for interfacing to SPARQL endpoints (web page links to RDFLib and JSON libraries)
xml-to-html.xsl stylesheet used by SNORQL to convert SPARQL Query Results XML Format to HTML for delivery to browsers
SKOS Simple Knowledge Organization System eXtension for Labels (SKOS-XL)
Serializing SPARQL Query Results in JSON Working Group Note
Regular expressions section of XML Schema Part 2 spec
Dean Allemang and Jim Hendler's Semantic Web for the Working Ontologist
Toby Segaran, Colin Evans, and Jamie Taylor's Programming the Semantic Web
Shelley Powers' Practical RDF
Tom Heath and Christian Bizer's Linked Data: Evolving the Web into a Global Data Space (free)