English Folk Dance And Song Society
Known to many as 'the EFDSS' and sometimes feared for being too highbrow, academic and stuffy it remains the focus for:
They have been based at Cecil Sharp House in London since 1930. They have an extensive library (named after Ralph Vaughan Williams) of collected material, publish a journal (The Folk Music Journal) and several books videos and CDs and have a hall available for hire.
It runs a wiki called Folkopedia which is a similar enterprise to this except it post dates it and it is run on peer reviewed lines.