I like to sew recycled clothing- it's cheap, low-pressure sewing. As far as I can figure, you either make something cool or you get rid of some clothes you never wore anyway!
This is a recycled-t-shirt skirt I made for a friend. It's a tiered, patchwork skirt. The pattern is adjustable for however much fabric you have (within certain minimums).
Step 1: Harvest Fabric
This skirt used 6-7 women's t-shirts. I only used the parts that were solid colors. Your needs will depend on the size, cut, and style of the shirts, and the skirt you hope to produce.
Cut them all into rectangles. Mine were mostly six inch squares, but you can introduce some variation in width as long as the height of each rectangle is the same.