Ok so as to avoid another thread of largely pointless contentious going issue, I'm posting this one in the this subforum, so only RM folk can respond.
My thoughts on this is to some degree influenced by NT Wright's analysis in his recent series of books on Jesus and Paul but I'm not sure i can do my idea justice.
Jesus was brought up with the Jewish stories that echoed within the community, that retold through the religous cermonies and festivals. A community that, although returned from exile in some sense, still longed for fullfillment of the promises of God and the great themes of redemption, kingdom establishment, a gathering of the people of God into all of his promises.
Jesus personalized those themes to himself, redemption was found in him, he would suffer for the redeemed people, he was the new law giver. In his ministry he uses the themes from the great Jewish stories to highlight his personification of Isreal's redemption within himself. The sermon on the mount is his giving of the law, his death is the destruction of temple, he multiplies bread and fish to a multitude like the provision of manna and quail.
His baptism could then be seen as his inaugatration of the new exodus of the people of God. It is after that inaugration that he calls his first disciples. Whereas our baptism is our identification of joining the people of God, and Jesus becoming our mediator. I clearly see this the beginning of our being part of the redeemed people that Jesus was calling out.