This one is fun and very easy.
I got the idea here.
you'll need: a plain t-shirt that you don't mind cutting in half, some ribbon, a safety pin, scissors and a sewing machine
lay your t-shirt out right side up
fold it in half, back sides together
mark down the middle line (this is your cutting line)
cut all the way up the front of the shirt
cut all the way around the neckline too
mark off the area between the neckline and the middle of the shirt and cut this will get rid of the corners - repeat on the other side
your t-shirt should look like this now
this next step is completely optional - I serged all around the "raw" edges
now we need to create a casing all the way around, mine is 1 inch, just a little bigger than the ribbon I am using
here is the casing, pinned all the way around
sew around to form the casing
thread the ribbon through using a safety pin
(I didn't cut it until after this step because I wasn't sure how long it needed to be)
figure out how long you want the ribbon by gathering the shrug...now you're done!