I made this last night using this tutorial. It took me less than an hour, and would probably be quicker for someone else. I am slow at sewing anyway and I was tired. Sorry about the poor quality picture, I used my webcam.
This is my new favorite tutorial! This t-shirt is one I've had for years, and it had a big stain on the front, right in the middle, which is now turned under for the casing. I really should have gotten rid of it years ago, but I hold onto random things, and now I'm glad that I did. Next time I would take the time to pin the casing down before I try to sew it, because it got a little bunched up going around the curve of the neckline. The nice thing is that you can't tell because it's all gathered up anyway.
I like this because it's cute and super feminine, but also very practical. It's made out of an old t-shirt so I can feel comfortable wearing it. This first one is a little rough, but I will be making more in different colors.
Seriously try this out! It will not take you very long, and it's super easy.