Learning Material
This excursus described ways how to enrich web pages with semantic metadata using domain specific microformats, RDFa , or microdata and schema.org.
More information can be found here:
Microformats: http://microformats.org/
RDFa: RDFa Primer 1.1, RDFa extractor
schema.org: Documentation, Live Microdata test
Web masters are able to test what Google would provide as rich snippet for their web sites - here.