I love this look. The turban headband popped up on runways all over the place in Spring 2011. Since I don't have $400.00 to buy one, and like to do things in "Reclaimed Wreckage" style, here's a tutorial on how to make one from a recycled T-shirt.
First, cut out two 5" x 22" sections from your t-shirt.
Fold them in half and sew. When sewing stretchy fabric without a serger, it helps to use a small zig zag stitch rather than a typical straight stitch. It allows the finished garment to stretch more without breaking your stitches.
Turn them inside out so you have two tubes. Next, we'll "link" them.
Lay one out flat, across the table, and lay the other on top of it to make a criss-cross.
Now, fold the bottom layer up, to link the two.
Fold the other side up.
When you pick them up, it should look like this:
Now, match the seams up, and sew the raw edges together.
You will be sewing through 8 layers of jersey at this point.
Finish your seam however you'd like and wear it with the raw edges facing in against your hair. All done!
In hindsight, I think I'd like to experiment with making it thicker, finding some stretchy lace, or embellishing it. But enjoy your new headband and take pride in knowing that you created it yourself from materials that would have been thrown out. Congratulations!