Metal, aluminum, or wood for a rack ?

Sorry!
One thing to actually do, is move the stuff AWAY from the speakers. A lot of folks have the stuff right next to, or in-between the speakers. Move your equipment away to a side wall. The amp can stay near the speakers.
Moving the stuff away does as much as an expensive equipment stand, as far as vibration goes. I have my equipment stands far away from the speakers. The Plasma and audio is closest on a side wall, with the audio equipment rack at least 12 ft away and out into the room a bit so I can always get behind it to swap wires etc. And then it is also close enought to reach the volume etc from my listening chair.. Then further away are the TTs.
I use a couple of fairly cheap audio/video equipment stands from a big box type store. They are square tube aluminum with glass shelves. I filled all the tubes with dried playbox sand. And all my stuff is on butyl rubber bottle stoppers. (size #10)
The bottle stoppers are a good combo for the glass shelves.
So I have a tall equipment stand for the audio, and a low/long one for video and Plasma, and another low/long one for two TTs. (the TTs are on the top with concrete patio blocks under the feet, with chemical mat rubber (probably butyl) cut to fit under the round patio bricks. The added mass helps out, and they are the furthest away from the speakers too. and NOT long side next to a wall.
If you do happen to go for a stand with glass shelves, dampening the glass is a good idea. either a product under, or over them.
My shelving cost like $150 each. and is a great value with the sand in the tubes. I am happy with my equipment shelving. (hah hah not saying THAT word..)

I have been researching looking for good audio racks, and i came across this:
http://www.audiav.com/

They have nice racks, worth a look.

BTw, wood and glass (tempered safety glass) racks are a good idea if you want a mix of style and build quality.

Elizabeth, you can say it if you want to.
I get a kick reading behind your gender thoughts on male preception.

I've decided to build my rack out of wood. With stackable shelving with spikes at the bottom of eack leg that will sit on the shelf below it.

I'm going to glue two 3/4 in. balsa plywood together to make a 1 1/2 in. shelf.

I'll make a three shelf rack at 24 x 18 in. with all the hardware for less than $150.

I can't afford to pay $$$$ for a rack. The wife wont understand. So, I do what I can.

It'll be better than the 1/2 in. thick MDF that I have now.

Thanks to all that has contributed.

John

Wood is out . Ive found metal with a 50/50 fill mix of sand and lead work well . I'm in the heavy and ridged camp , although many are using the less mass method . Any solid ridged stand will be a improvement .