Basic RDF support is part of Drupal core. When the RDF module is enabled, Drupal outputs RDFa (RDF in attributes) for things like node titles and date created. To expose field values using RDF, you need to use the RDF Extensions (RDFx) module. Here’s a YouTube tutorial on how to use RDFx.

Here’s a tutorial on how to index RDF data and provide a SPARQL endpoint, using the ARC2 Store module (which is minimally used and poorly supported) and RDF Indexer.