The conclusion of John Piper's chapter, Making Much of Christ from 8 to 5, in Don't Waste Your Life (the chapter begins on page 131):
"In conclusion, secular work is not a waste when we make much of Christ from 8 to 5. God’s will in this age is that his people be scattered like salt and light in all legitimate vocations. His aim is to be known, because knowing him is life and joy. He does not call us out of the world. He does not remove the need to work. He does not destroy society and culture. Through his scattered saints he spreads a passion for his supremacy in all things for the joy of all peoples. If you work like the world, you will waste your life, no matter how rich you get. But if your work creates a web of redemptive relationships and becomes an adornment for the Gospel of the glory of Christ, your satisfaction will last forever and God will be exalted in your joy."
I'd give the entire chapter a read; I don't sense that Christians do enough thinking about how their "ordinary" work can display the worth of Jesus.