Cut the T-shirts into strips. I made mine 8" wide, but you can use any width you want. Also, I cut my strips horizontally to highlight the t-shirt's designs, but cutting vertically will work just as well.
Select two strips to begin with...
and pin them right side together on one of the short sides.
Sew along the side you pinned.
Keep repeating this process until you have two pieces that are the length that you want the scarf to be when it is finished.
With right sides facing each other, pin the long sides of the two pieces together and sew, making sure to leave the ends open.
Turn the scarf right side out and stitch the ends closed about two inches from the bottom. In this photo, my pieces are two different lengths. I cut the green piece to even them up after I sewed the end shut. No worries!
Make fringe at the end simply by cutting slits with your scissors.