Alice at futuregirl has a great tutorial on how to do seamless single crochet.
I love making seamless crochet stuff. It’s great when I make the last stitch in my crochet item, and it’s done. Joining can be such a pain. Since I can’t find instructions anywhere (do you know of any?) that explain how to make something seamless, I’m going to publish the method I settled on after much trial and error. The following instructions are for single crochet.
Read Alice’s tutorial on her futuregirl site here. – Link.