I started with one of my old t-shirts, cutting 1 1/2 in wide strips from it.
Using the longest stitch, I sewed right down the middle of each strip.
I ruffled each strip by pulling the bottom thread and easing the gathering along the thread. This takes a while so I sat and watched a couple of episodes of Veronica Mars while I did it. I really miss that show.
I laid out one of my husbands old dress shirts and started laying down the ruffled strips to see how wide my pillow would be and to make sure I had enough ruffles to go all the way across the shirt.
Once I had all the ruffles down, I knew how wide to cut my pillow.
Using the side seam of the shirt as a guide, I started sewing the ruffles on to the back of the shirt, going down the center of each strip, right over the original basting stitch. I overlapped the ruffles just slightly.
Here it is with all the ruffles attached.
Turn the shirt over and button up what is now the back,
then turn the shirt inside out and sew the top and bottom of the pillow.
Unbutton the shirt and turn it right side out.
Now you can either stuff it, or make a pillow form to fit inside, ( I did this using an old sheet and the filling out of an old pillow.)
Once the pillow is stuffed, button up the back, and enjoy your up-cycled pillow!