For the past few months, the computer I use for my rapid prototyping station has looked like this. No tower, just a motherboard, power supply and hard drive in a pile. I finally got around to creating a slightly less precarious setup.
I grabbed a sheet of cast acrylic for about 10 bucks from Home Depot.
I cut it into squares, and drilled holes to accommodate four foot-long 5/16" threaded rods (about $2 a pop from Local hardware store).
Using zip ties and 6-32 bolts (these are compatible with most CPU tower components) I secured each item to its own "shelf" and bolted said shelves together with the threaded rod.
Not the most novel solution, but it'll do just fine for now. Also made for a good excuse to update my blog, as I've had little time to work on anything else this week.
Upgrade to rapid prototyping station complete.