My wife & I have done several holiday layouts using D56/lemax items + O scale trains. We built 4 4'x4' tables and use them in various arrangements based on the design for that season. I line them up and clamp them together. Sometimes we insert lowered areas between these main tables for water scenes. We ended up just drilling lots of 1/4" up to 1" (or larger as needed) holes in the table tops wherever needed to drop down the various plugs for buildings/etc. On our ealier layouts, we would try and route all the cables to one point and drop them down. This proves tricky and hard to hide the cables. So now we just drill new holes if needed or using existing ones that are already in our table tops. Some builds/accessories/etc have modular "bricks" with a detaching small plug and thus don't need the big holes, but some items still plug directly into your 110 AC and thus you need big holes. You end up with "holey" table tops, but the more layouts you do, the less likely you are to have to drill a new hole!
Anyway, once all the wiring is dropped down under the table, I get (LOTS of) those power strips that have 8 or so little pigtail plugs instead of a straight power strip. Like these:
http://www.amazon.com/Accell-D...words=octopus+outlet
The advantage of these "squid" deals is that you don't waste sockets due to the bricks' size. Power strips always end up with wasted sockets.
Next you hide everything under the table with a skirt. We buy the cheap-o plastic ones at the part store and cut them to fit. For halloween, we do black, for christmas, we do red or green or even white.
On top of the layout, you then cover all the holes, any wires exposed, etc, with whatever ground cover you're using. We use various autumn colored foams for halloween, or snow for winter scenes. And lots of trees, people, roads, etc from D56/Lemax.
We've also used white butcher paper crumpled up to do mountain sides that look like snow covered mountains. It works great and is fairly cheap and easy to do.
Here are some pics of previous layouts we've done.
http://aoot.com/pics/Christmas_2005/
http://aoot.com/pics/Halloween_Layout_2007/
http://aoot.com/pics/Halloween_2007/
http://aoot.com/pics/Christmas_Layout_2008/
http://aoot.com/pics/Halloween_Layout_2010/
http://aoot.com/pics/Halloween_2010/
Hope this helps!