GWAS Central now provides data in Semantic Web and Linked Data compatible formats through:

• Individual markers, phenotypes and results which now output RDF and Turtle formats that connect to Linked Data resources.
• Nanopublications: a  Semantic Web resource using named graphs, and contain key results for each dataset outputs N-Quads format. These follow the nanopublication proposals suggested here.
• The construction of a triple-store with a SPARQL server available at http://fuseki.gwascentral.org.

We are in the process of updating the Web Services section of our help with more information.