How can I make an attractive enclosure for my circuit?

My two favorite places are OKW Enclosures and Polycase. They have off the shelf options in different styles, no minimum order. They will even do customization on small orders too, i.e. drill holes, silkscreen, etc.

If you can't wait and you are lucky enough to live next to a Fry's electronics, you can walk over and pick up a simple one for not much extra overhead.