I have a deep nook that is 92 inches wide and I needed a workstation for my computer and my sewing machine. I was inspired by the modular desk I saw at Pottery Barn. But I didn't want to pay that price.

I made a desk out of two filing cabinets and a wood top. I found two white wood filing cabinets with sea grass baskets for drawers. Went to the hardware store and had them cut plywood for the top. Purchased some wood molding for the edges. The desk is slightly deeper than the little filing cabinets. I attached the molding, put the cabinets under it and left a small gap at the back to thread up cords. Painted it all white to match the cabinets. My top is actually a double thickness of the plywood and it is so heavy I didn't have to screw it to the bases. I put my computer behind the one of the filing cabinets and the sewing machine behind the other. Because I paid the extra $2/ cut at the hardware store, I didn't need any tools other than a hammer to nail the layers of plywood together and attach the molding. If you don't have somebody to hold things in place for you, then pick up a couple of clamps at the hardware store.

Originally, I was trying to find some cheap ugly cabinets but I couldn't find any at the time. The idea was the same but would have a fabric curtain attached behind the molding to hide the cheap cabinets.

The next step for my desk when I get more time will be to create a bookcase at the back of the desk. I have a fairly deep nook where this is located.

Laptop?

The best thing to do would be to have a counter-like workstation and mount the towers under the desk. You don't want to completely enclose the towers in anything because they need to have air to vent or the computers will run hot, overworking the cooling fans and shortening the life of your PC.

Simple, turn them sideways (lengthwise) against the wall behind your monitor(s). Attach all your cables, etc. to your computers and monitor. Buy a full sized sheet of foam-core board. You can get it in black or white and either leave it alone or cover it in cork and/or wallpaper. Add a small piece of Velcro to the sides of your computer and to the back of the foam-core. Attach the foam-core to the computers. It's easy to cut out areas for your cords but it hides everything. However, it allows air flow, easy access to the computer and no visibility. It's an easy win-win. Good luck.

Zilla-Mama, most PCs vent out the sides as well as the back, and sometimes even the top. I really wouldn't recommend directly attaching the foam board to the PC, but doing something like this and having it "raised" over the PC would be okay. This would only work if you don't necessarily need easy access to your PC's drives. I just hate to see people overwork their PCs and get less life out of them for the sake of design.

@ Toypixie - it's easy to make standoffs for the foam core: Cut squares and stack them to make legs. |||| 4 layers would make a good standoff to allow airflow behind the foam core.

Something you could also try is reverting to the old school way of putting the CPU under the monitor, often towers can be placed on their sides safely.

You could also build a cabinet or enclosure to divide the desk in the center and setup keyboard/monitors on each side of it.

here is a great picture of someone who mounted their towers under the desk.
http://www.flickr.com/photos/blupics/2293532220/in/photostream/