We had t-shirts, hats and notebooks available on cafepress for about two years, and sold a grand total of.... three. The only notebook that sold was to me.
We pulled them down over the summer, since the cafepress store wasn't worth maintaining, and character shirts obviously don't sell well for us. We are looking at doing some shirts printed locally, but it'll have to be a design we know we can sell at least ten of, in order to cover costs, and we haven't hit The Platonic Ideal of YAFGC t-shirt design yet.