Apparent Contradictions: Does the Changeless God Change His Mind?

We've all heard that the Bible has contradictions.  I've been taking some time to debunk some of them and you've voted this next one in today.  So feast your eyes on these next two verses and think about them for a moment.

God is not a man, that he should lie, nor a son of man, that he should change his mind. Does he speak and then not act? Does he promise and not fulfill?  --  Numbers 23:19


When God saw what they did and how they turned from their evil ways, he had compassion and did not bring upon them the destruction he had threatened.  --  Jonah 3:10

Theology Thusday: Does the Old Testament Teach the Trinity

A few months ago, I got an E-mail from a friend.  He quoted Genesis 1:26 and asked me who is the "us" mentioned.  That got me talking to him and a few other people about the Trinity and the Old Testament.  Does the Old Testament teach the Trinity?  If not, then why not?  If God really is one Being who eternally existed as three Persons, then why would He not feel like mentioning that in the Old Testament?