Ponoko does metal now, however, just to set expectations the smallest material is about $30 US. Then you have to add the costs for cutting (and shipping.)
What are some good sites that would offer near-exact box measurements, precise cuts in the top panel (circular and rectangular), and engraving/printing if available?
If you are looking at a small quantity (<100) then a cutting service like Ponoko is probably your only option. (Ponoko isn't the only option, there are others, that's just the one I prefer.)