poshRDF is an approach (and, as a by-product, an RDF-in-HTML syntax) to efficiently extract RDF from (many) microformats and similar, ad-hoc POSH markup. The generated RDF is a single-namespace (intermediate) triple representation that can be converted to deployed vocabularies such as FOAF, iCal/RDF, vcard/RDF, or RSS 1.0 in a post-processing step (more on the esw wiki).
It's also possible to use the POSH definitions and create an RDF Schema from them (see below).