Plaid Cymru (literally 'the party of Wales') is currently holding its annual conference in Aberystwyth. The party was formed as long ago as 1925, but its political significance grew only in the 1960s. It was in the Carmarthen by-election of 1966 that Plaid stunned the political world and won its first seat in Parliament. The MP elected was Gwynfor Evans, the President of Plaid - who was instrumental in developing the party.
In recent years, particularly after the creation of the Welsh National Assembly, Plaid Cymru has played a major part in Welsh politics - at all levels of government.
Its website is http://www.plaidcymru.org/content.php?lID=1