One of the ways we get RdfCalendar data is scraping from XHTML.
For example XHTML to RDF to iCalendar, Ryan Lee (with DanC), March 2003. The approach details the use of XSLT to transform valid XHTML to RDF. It helps if the XHTML has hints in the form of class or rel attributes to denote what information is where, avoiding abuse of the structure of the document.
LibbyMiller uses Perl sometimes. for example... ?