I could and would never wear half of the t-shirts that I get at races. What I would use is more reusable shopping bags. Problem solved: turn on into the other!
After choosing your shirts, lay them out on you work surface.
Cut off the sleeves, preserving the side seams.
Use a template to shape the opening around the neck.
Cut around template. I used a bowl.
Mark the bottom where you are going to sew the short shut.
I also decided the angle some side seams so the bag would be
wider on the bottom. The angle sides serve as a psuedo-gusset.
Sew along your markings. I did two hems around each
side for added stability.
I filled one with running gear...
...and used the other for some groceries.
You can keep the memories with these great shirts,
but use them more frequently and usefully!