Can someone please explain the Duchess of York's speech "Dead life, blind sight..." from "Richard III"?

DUCHESS.
So many miseries have craz'd my voice
That my woe-wearied tongue is still and mute.--
Edward Plantagenet, why art thou dead?

QUEEN MARGARET.
Plantagenet doth quit Plantagenet,
Edward for Edward pays a dying debt.

QUEEN ELIZABETH.
Wilt thou, O God, fly from such gentle lambs,
And throw them in the entrails of the wolf?
When didst Thou sleep when such a deed was done?

QUEEN MARGARET.
When holy Harry died, and my sweet son.

The women in "Richard III" act a lot like the women in Greek Tragedy, which basically means a lot of wailing and a lot of mourning. In this scene, the women all get together to mourn the way that the Wars of the Roses - and particularly Richard himself - has put the men in their lives into the ground. Sons, fathers, husbands, brothers have all gone missing - are all dead. And the women are exhausted with it.

DUCHESS.
Dead life, blind sight, poor mortal living ghost,
Woe's scene, world's shame, grave's due by life usurp'd,
Brief abstract and record of tedious days,
Rest thy unrest on England's lawful earth,
[Sitting down.]
Unlawfully made drunk with innocent blood.

So the Duchess of York is talking about herself and how miserable her life is, in a series of antitheses. Her life is like being dead, her seeing is like being blind... she is like a poor ghost, though she is mortal and living... why? Because her world is a scene full of woe and shame, and she feels that she is the "due" (the thing owed to) the grave, because her life has been usurped by sorrows: by the death of all of her family (except Richard, her son).

She is the brief abstract and record (a written version of something) of a horrible family history. Her life, in short, has been ruined, and is a misery. And at the end, she decides to rest her unrested (i.e. troubled) soul on the earth.

Hope it helps!