zzounds.com, sweetwater.com, samash.com, musiciansfriend.com plus a zillion other places sell Middle Atlantic Products (MAP) rack rails which are fairly inexpensive, and very thing, so the edges of your equipment are about 1/16" away from the wood edge. I built my producer's desk/synth rack this way, and it came out fairly nice.
I agree that steel rack rails are extremely durable if you intend to move gear around (I'm always buying, and selling on ebay so this survivability was important to me).
If you need a lot of rail length, or multiple rails and like the DIY method of doing even this... an old computer or relay rack works very well. Put a metal cutting blade into your table saw and start hacking away. Typically, a 8' relay rack (aluminum) sells for about $40-50 used, and for that price you get two 8' rails, which allows you to mount 42U single space units.
Cut 'em in half, fourths, 10ths, whatever floats your boat. Then, to be really stingy, cut them lengthwise and get four rails instead of two! Most computer/relay racks have threaded screws on the front, AND the back of the rails. This is because the rails are actually made of extruded "C" channel, rather than a simple angle iron.
My last home studio in connecticut was this way.... I took two aluminum relay racks and cut them lengthwise down the sides, giving me four racks, 42U a piece. Sad thing is, I still had a pile of gear on a piano bench. See, I used to have a "vintage gear" fetish, so I had to have one of everything 10+ years old. Of course I still have that fetish, I just spent a lot of time sampling those units before selling about half of them on e-bay.