Why does God command the Israelites not to boil a goat in its mother's milk? Some of the laws I can directly see why they were given, however I do not understand the last part of the verse below regarding not boiling a kid in its mothers milk.


  Deuteronomy 14:21 NIV Do not eat anything you find already dead. You
  may give it to an alien living in any of your towns, and he may eat
  it, or you may sell it to a foreigner. But you are a people holy to
  the LORD your God. Do not cook a young goat in its mother's milk.


What does this law mean really, is there some spiritual significance I am not getting?
There is much debate about this one but I think the Rabbis never understood it, which causes trouble to some Christian commentators as well.  It reminds me of this:


  For it is written in the Law of Moses:“Do not muzzle an ox while it is treading out the grain.” Is it about oxen that God is concerned? (1 Corinthians 9:9, NIV)


The Apostle applies this to establishing an argument that ministers should be paid for their effort. A prohibition is there about an animal but for the purposes of how we treat each other.

In this case about a goat and its mother, the lesson is we ought to respect the tender relationship of an animal and her young. The law is established about less important things to make a stronger point. God honors the relationships of a goat and her child.  How much more than should we honor the relationship of parents and children? We should not despise relationships that God honors so strictly.