I've been preaching about the Kingdom of God for a long time. I recently ran accross this description in a Bryan McClaren book and thought it was pretty tight.

The Kingdom of God is available to everyone, starting now. When Jesus refers to the Kingdom of God, He doesn’t mean something that happens after we die, far off in heaven; He equates the kingdom of God with Gods will being done on earth as it is in heaven. So the kingdom of God is life as God intends it to be – life to the full, life in peace and justice, life in abundance and love. Individuals enter the Kingdom when they enter into a relationship with the Liberating King, when they trust Him enough to follow His ways. But make no mistake, the Kingdom is about more than our individual lives; it is abut the transformation and renewal of all God has created. It may start with our individual responses, but it doesn’t stop there.