Is it generally acceptable to mount arduino's, power supplies, etc to wood? I'm not talking about high power equipment in this case. Just various arduino type boards and 120V/12v/5v (maybe 100 watts?) I know tv's cabinets used to be made of wood but the "circuit boards" were generally inside a metal chassis. Do you need to provide a barrier between the boards and wood? This will be totally encased in wood but vented.
wood doesn't conduct electricity, however any sap or water with-in the wood casing you are using will. I have heard of people using hot glue guns to insulate exposed pins and wires. Haven't tried it myself but it seems reasonable.
I realize wood doesn't conduct well. I was wondering if typically you have to consider fire hazard from overheating components.
You had me till 120v, 100w.
120v, 100w, wood...
Those lines only intersect in -- Calamityville.
UL-Listed NOT!
I could mount it all in a plastic box and mount the box to the wood. Plastic doesn't seem much better as far as a fire hazard goes but that's done all the time. What makes plastic acceptable? Anyone know?
Ya the amount of wattage you are running may cause an issue. I think as long as your components are rated for the current and power you should be ok. Heat shouldn't build up unless your components aren't strong enough to handle it. That includes your wire.
Something like this?
http://forum.arduino.cc/index.php?topic=158392.0
I do it all the time. The original breadboards were actual boards, you know 
I do use standoffs, not because of heat but just to ensure the board is level.
I've seen a couple projects built in bamboo boxes which look really nice.
I love using wood.. it's a great material and basically free here In The Woods In Vermont. Here's an ex-tree which is becoming the base for my home automation system reincarnation on a Mega2560:
It has a coat of Polyurethane and I'll run 24VDC max here. It will drive two Opto22 racks with 16 inputs and 16 outputs to a bunch of home devices. That part is already there; I am replacing my IBM AT based Turbo Pascal system I wrote 20 years ago with the Mega. Here's a photo with the terminal strips connected to the Mega Sensor Shield:
This kinda answers the question, "What would anyone do with all those I/O's on a Mega??" 
That's basically what I want to do. Thanks folks!
The issue isn't whether it's made from wood or plastic, but how hot it makes the wood (or plastic). There is no problem putting a 2kW radiant heater on a wooden floor because the floor doesn't get too hot. But a 100w lamp might start a fire if it is touching a wooden beam.
...R
Looks somewhat relevant...
http://www.fpl.fs.fed.us/documnts/fplmisc/rpt1464.pdf
With prolonged exposure at all of the temperatures used there was a gradual darkening of the wood, accompanied by loss of weight and shrinkage in the trans-verse dimensions of the specimen.
...
Samples which had been exposed to 107°C. for 1,050 days assumed a light chocolate shade.
Obviously, you need to ensure the wood temperature will always be well below 107°C. And, you need to ensure good ventilation in case a problem occurs with the first condition.
That can't be true or these would not be available...
https://www.google.com/search?q=100w%20in%20ceiling%20light
I understand that it depends largely on where the 100w is being dissipated. Mostly into the wood is not a good thing. Mostly into the air and vented and you are probably ok. I wanted to make sure that it was acceptable assuming there was no heat issue.