1. Open a new Illustrator web document (624*351). Using the Rectangle Tool(M) draw a rectangle that covers the entire artboard. Fill it with a light grey->white gradient and lock the layer.
2. Still having the Rectangle Tool(M) selected draw a square (holding SHIFT). Make this square whatever color you like and apply a white stroke (the width of the stroke depends on the size of your square).
I've used this stroke:
3. Duplicate the layer containing your square. Use Effect->Path->Offseth Path and change Offset 10px (you may need to change this value if you're square is bigger/smaller). Now, choose the fill color of this layer to be "none" (that red-slashed white square from the swatches panel).
For the stroke use this values:
At this stage, if you want, you can choose to expand this two layers.
This is what you should have:
4. Here comes the fun part :D . Select all the squares and group them, select the group and go to Effect->3D->Extude&Bevel, check the "Preview" checkbox and move the Depth slider until you're pleased with the result.
Here's the result:
5. Having this shape created you can duplicate it to make some cool designs. Keep in my that you'll have to change the Layer order of this shapes. Here are the shourtcuts aranging the layers:
CTRL+] -> Bring Forward
CTRL+[ -> Send Backward
CTRL+SHIFT+] -> Bring to Front
CTRL+SHIFT+[ -> Send to Back
Another greate Shortcut is CTRL+D (transform again) which is very useful for creating this:
6. You can use Direct Selection Tool(A) to select the red squares and change their color. You can also add a shadow (by creating a black shape using the pen tool and applying Effect->Blur->Gaussian Blur).
PS: You can also apply gradients on the squares.
This method can be used to create many other designs... I don't know, you should try using this method on circles? Or applying some different strokes,or addying some final-touch reflections,etc... it's up to you.
Comments are wellcomed!