Zadok the Priest...

I note that my post below has attracted a comment from the Old Oligarch, whose 'blog is the first I ever read. Now, he is a real theologian, as opposed to myself who just pretends to be one on the internet. That's why I can't answer his questions with anything more than a shrug of the shoulder. I thought that the generally accepted theory was that the Sadducees derived their name from Zadok, but beyond that I don't know.
Regarding the use of Psalm 110 (Dixit dominus), I'm no exegete. What I do note, however, is that it is used by Our Lord in his discussions with the Pharisees.

Now while the Pharisees were gathered together, Jesus asked them a question, saying, "What do you think of the Christ? Whose son is he?" They said to him, "The son of David." He said to them, "How is it then that David, inspired by the Spirit, calls him Lord, saying,`The Lord said to my Lord, Sit at my right hand, till I put thy enemies under thy feet'? If David thus calls him Lord, how is he his son?" And no one was able to answer him a word, nor from that day did any one dare to ask him any more questions.

I'm inclined to think that the way in which Christ used the scriptures Himself bears study. (I also note that the Vatican website includes the following commentary of Pope John Paul II as part of his series of reflections on the Psalms and Canticles of the office.)
On a mostly unrelated note, part of the reason that this 'blog is so-called is because (unlike Melchizedek) Zadok has the honour of having his theme tune composed by Handel. (Link from Fine Arts Brass) This stately piece has been used at all British coronations since that of George II in 1727. I'm no fan of British royalty, but I have to admit that they seem to have taste in these matters, the funeral of the late Princess Diana excepted. I seem to remember reading that the rite of the Coronation of a Monarch is the Anglican liturgy was the one ceremony virtually untouched by the reformation (perhaps one of my knowledgable Anglican visitors could confirm...). I also seem to recall that for the coronation of Elizabeth II in 1953 both the firm which traditionally prepared the oil and the recipe for preparing said oil had failed to survive the blitz, and that the concoction they eventually came up with for the ceremony was said to have been 'foul-smelling'.
The Oligarch's question regarding the Saduccees and the possible etymology based on 'tsaddiq (righteous)' also reminds me of the Hasidim, a branch of Judaism primarily found in Eastern Europe. It is said that 'Hasidim' means 'the righteous', though Martin Buber suggests that 'those who keep the faith' is a better translation. Indeed, it is through Buber and his delightful work tales of the Hasidim that the parables and stories of this extraordinary group are so well known. It's a great book to flick though and the stories seem to provide enlightenment and puzzlement in more-or-less equal measure. Amongst the less obscure tales we have the following:

The Greatness of Pharoh
Rabbi Levi Yitzak said:
"I envy Pharoh! What glorification of the Name of God did his stubbornness beget!"