Sharon at Early Modern Notes has provided a link to the Mabinogion as translated by Lady Charlotte Guest. I haven't read all of them (although I've come across all of them in summary form at one point or another), but I have read, and have always enjoyed, Taliesin. How can one not like a story of a young man making the old bards go "Blerwm, blerwm"? It's been a while since I've read it, though; I was virtually certain that the song that begins, "Primary chief bard am I to Elphin," had the line "I am a word in letters"; but it doesn't. I was confusing it with another work, the much earlier Book of Taliesin (in particular, the song of the Battle of the Trees). I did remember a number of other lines in it, though (particularly "I am a wonder whose origin is not known"). I like best the song on what the bard should know, though:
The Excellence of Bards
What was the first man
Made by the God of heaven;
What the fairest flattering speech
That was prepared by Ieuav;
What meat, what drink,
What roof his shelter;
What the first impression
Of his primary thinking;
What became his clothing;
Who carried on a disguise,
Owing to the wilds of the country,
In the beginning?
Wherefore should a stone be hard;
Why should a thorn be sharp-pointed?
Who is hard like a flint;
Who is salt like brine;
Who sweet like honey;
Who rides on the gale;
Why ridged should be the nose;
Why should a wheel be round;
Why should the tongue be gifted with speech
Rather than another member?
If thy bards, Heinin, be competent,
Let them reply to me, Taliesin.