http://www.ltg.ed.ac.uk/helpdesk/faq/index.html
and there's a page of corpus pointers on
http://www.ltg.ed.ac.uk/helpdesk/faq/Texts-html/general.html
The discussion seems as if there is demand for an expanded version
of this, possibly renamed as a corpora FAQ. If CORPORA subscribers
are willing to send suggestions for expansion, I will collate them
and post a pointer to the improved FAQ back to this list.
Chris