a great men's shirt makeover into a skirt. This is very doable with the right shirt. Tutorials, photos, suggestions at the link. I would follow most of the instructions, but would leave the bottom open a few inches for walking ease, and interface the waist.
Another T-Shirt Refashion: Tank Top I especially like the polka dot straps. I think she used ribbon or something, but I might use fabric paint to make the excess fabric from the tee polka dotted (so the color matches exactly) & then use it as a ribbon strap.