When I first started Curiously Contrary, I was predominantly making and selling crocheted items using t-shirt yarn, including bags and door stops. As part of this, I wrote a few of my own patterns, which are available for you to purchase as downloadable pdf files.
Crocheting with t-shirt yarn gives a lovely chunky look, is quick to do as the stitches are large (and easy to see) and it is much less fiddly than crocheting with regular yarns. Great for beginners or those that find regular crochet too slow, fiddly or tedious.
If you don't have t-shirt yarn, you can buy it ready made (I like Tek Tek yarns) or you can have a go at making your own from actual-shirts. (Here is a good tutorial to follow: https://www.youtube.com/watch?v=e-UOc9RHdAY )