How do you take your Arduino project to mass production? (or mass-ish)

It really depends on the type of components you are using in your end product. Most things will be SMD components. This means a smaller package, but much more difficult to solder. You can however get through-hole components. These are pretty much the type of components you used in your prototype, but you end up soldering it to your board. Depending on your client base you can always sell your product as a kit, assembly required.