This is quite a collection of items gathered from various sources.
Wales Timeline 1000 BC - 1977 AD.
Welsh History : A Short Bibliography.
Gildas. De Excidio Britanniae (On the Ruin of Britain).
Medieval Welsh literature. From: Wikipedia.
Annales Cambriae. From Wikipedia.
Nennius: Historica Brittonum (History of the Britons).
The Mabinogian : books 5 to 8.
The Welsh Triads.
Knights of the Round Table from the Welsh Sources.
Trioedd Ynys Prydein (another translation of the Welsh Triads).
Mostyn manuscripts : Mostyn MS 117
The Picts : The language of the Picts.
The faith of the English kings. By : Hugh Bibbs.
Of course they are translations, but are an amazing group of articles.
For a discussion of Welsh genealogy see http://welshgenealogy.blogspot.com .