Here we review sites concerning widely used data formats to decide on a prioritised list of formats we want to cover with the RDF2x work.
Rough list of most popular formats, based on a quick look at publicdata.eu, thedatahub.org, and data.gov.uk:
XLS and CSV are the most popular formats on all three sites (ignoring RDF and SPARQL on thedatahub).
PDF and HTML are also popular on all three sites.
Plain Text, .doc, PowerPoint and JSON are only really in significant numbers on data.gov.uk, they're present in relatively small numbers on publicdata.eu and thedatahub.org.