Lyfrau o'r Gorffennol or Books from the Past is a growing online collection of books of Welsh cultural interest which have long been out of print. Some are in Welsh, some in English, all are available to download in a variety of formats or to read online. Found as the collection includes a book on the Adventures and Vagaries of Twm Siôn Cati, the famed bard, genealogist and bandit trickster supreme from Tregaron. It's one of a host of well-presented digital archives built using the multilingual open source Greenstone software suite.
The poems of Dafydd ap Gwilym A project at Swansea University puts the works of one of mediaeval (14th century) Europe's literary giants on line in full, including a full concordance, digitalised manuscripts, English translations and recorded readings. Dafydd was a great poet of love, lust and nature and a master of strict form. His work was also hilariously funny.