Why would God allow Suffering?

Why would God allow so much suffering and evil? If God is so loving and powerful, why would he allow so much suffering and evil to happen? Why doesn't he do anything about it?

Other Helpful Stuff:
Romans 8:18-39
John Piper – sermon text – The Suffering of Christ and the Sovereignty of God
John Dickson – short article – How to answer people who ask: “Does suffering disprove God’s existence?”
Don Carson – book – How Long O Lord
John Dickson – book – If I Were God, I’d End All The Pain