You can also fringe the sleeves.
These two are made from the same shirt. For the necklace (or belt) we cut off the bottom hem, then cut around and around so we had one long continuous strand about 1" thick. We cut that into thirds and braided them, then added chunky wood beads that have been sitting around forever.
We didn't want to waste the top picture, so we used fabric glue to attach it to posterboard, then added jewels and glitter. This would be fun to do with a t-shirt that had a funny saying, or a favorite rock band on it. We are trying to find our scrap cork board to make a bulletin board this way.
We had seen ideas for shopping bags that required sewing the bottom, but then Karl from Tulsa sent us this idea - just fringe and tie the bottom. That looks even sturdier than sewing. Use strips from the sleeves as added handles. We left the hem on, but you can cut that off and add pony beads to the bottom.