I bought a bunch from Jennifer's Jewels on Etsy. http://www.etsy.com/shop/JennifersJe...ef=seller_info
They were sew in. I am not a sewer at all, so I just tacked mine in by sewing one stitch over itself 4-5 times at one end of the label. It worked and they stayed on. The labels were still very readable 18-20 months after I sewed them in. They were washed probably once a week sewn into DD's daycare clothes. The fabric the labels were on became worn, but did not develop holes or break down to the point of coming off. I have the feeling that if I had sewn the labels in appliqué style (all the way around), they would have held up better. Mine were flapping the wind. But I think that 20 months of readability is pretty good. The only reason I cut them out was because DD outgrew the clothes and I was giving them to someone else.
HTH!
Mommy to my One & Only 05.07