Take an inexpensive t-shirt and deconstruct it with safety pins
Followup (3/23/13): I like to imagine I influenced this design with this instructable. (Though I'm probably just tuned into some trend somehow)
Step 1: Materials
40 safety pins all the same size
one inexpensive tshirt
super glue maybe?
Step 2: Cut Twice
cut the tshirt once through all layers across the middle just under the bustline
cut it once through the top layer from the middle of the neckline down to the bottom
Step 3: Pin Together
pin the tshirt back together with safety pins. about one every two inches along both cutting lines. This tshirt took about 40 pins. 10 along the front horizontal, 10 along the back, 20 up the front vertical.
Step 4: Finis
I like how it looks like a shower curtain.
Okay, this is not a serious garment, but if you were to wear it for realz, you might want to do something like super glue the safety pins shut so they don't come undone and stab you one random day...