I was surfing today and ran across this site:
www.spreadshirt.com
I wouldn't have mentioned it except for they do transfers of image files onto t-shirts. I am thinking about getting one of Roxy made. I wouldn't have thought much of it, but my brother, who is in the screen printing business, says their process is "a good one".
I've tried those print and iron sheets, but the design always cracks and looks homemade-y.