I found a great site called J Caroline Creative and it has lots of how to's on some really fun projects. This is a pillowcase that I made using the directions from their site and you can get the directions here. It is really easy to sew up and you can do a few variations on it. And it is definitely easy enough for a child or teen to complete as well. =)
Take a look at some of the other how to's as well as they have instructions for pillows, curtains, aprons, bags, baby items and even some alphabet applique templates to print out!