Talk to your local building inspector. When I was preparing to put in a sub-box a few years ago, I had a meeting with my inspector first. He was able to tell me exactly what would and would not pass inspection. You also want to be sure and pull a building permit and have it inspected or you might have problems with your insurance company if you ever have a wiring related claim in the future.

Conduit is a local code. In Chicago you need conduit.
You also need proper clearances in front of the panel. You need a clear space 30" wide, 36" deep and 6'7" high in front of the panel. That means no counters, shelves, washers, dryers, etc in that space.

As for the conduit question, I used to live in Chicago and dealt with that Chicago Code requiring conduit for ALL electrical wiring, which is absolutely ridiculous. (As I have mentioned in other threads, I call it the "full-employment electricians' union code" because it merely entails that electricians do most of the electrical work because it is too much of a hassle for DIYers).

Elsewhere, conduit is generally required ONLY for exposed runs (outside of walls or ceilings) so as to protect it from being snagged by anything. (For instance, I took down the drywall from my ceiling and exposed the beams, and I needed to run the circuits that ran through the ceiling through metal conduit instead of the NM cable that was there.) For everything else, you can use ordinary Non-Metallic (sheathed electrical cable-like) cable inside the wall. Just make sure that the gauge is sufficient for the amperage carried by the wires.

[This message has been edited by Lawrence (edited December 27, 2003).]