I cut apart a Levi's denim shirt to make into jeans, and two boy's shirts with tiny plaid for shirts. And a really pretty, fine purple corduroy jumper to make into two doll dresses.
Doll shirts aren't the easiest thing to make, as they have to be made just like human-size shirts, but in miniature - with tiny collar and neck band. And so many of the doll shirts I see out there aren't quite right, with the collar being way too high in front. So, maybe a shirt pattern would be welcome.