SIOC data I use to crawl
Crawling the web for SIOC data (which are most often provided by SIOC-enabled sites) needs a starting point, a so called plan file. I use one which is barely based on the wiki page found above, it is here. The format of
rdfs:seeAlso is documented as recommended by DanC on ESW Wiki
[Alex is providing a webservice that transforms SIOC Wiki pages to RDF/XML], this way one will get an up to date list of SPARQL endpoints and SIOC-enabled sites.