Editing Note: the original website is no longer available. For similar content, try the St. Catherine of Siena site in Phila., Pa.
Directly quoting from the original website at http://www.caterinati.org.uk:
The Society of St. Catherine of Siena is committed to the renewal of the intellectual apostolate in the Roman Catholic Church. The Society has an association with the English Province of the Order of Preachers. It is registered charity number 1088118.
In particular interest, this Fall the Society of St. Catherine of Siena will launch a new journal: Usus Antiquior. More information on this initiative has been posted by Mark at the above linked post to his website.