First ones to come to mind are
href="http://www.horrorshirts.com/">http://www.horrorshirts.com/ and
href="http://www.fright-rags.com/">http://www.fright-rags.com/ .
There is a seller on HorrorBid that has some cool degns.
I prefer inde, small run, limited edition tees myself, but those are a right place right time kinda thing.