Challenges when Bringing Hardware to Market?

sandbenders asks: "I'm interested in building a product that would be of interest to some Slashdot readers (in other words, it's full of geeky goodness), and I have had great luck finding companies to help me build my design. It uses electricity, obviously, and I know this means that it has to be inspected, listed, etc. by the appropriate bodies. Does anyone have any advice for how to get this process completed, what costs to plan on, or other advice for someone starting up a business of this type?"