Edited to add: PS. There's also a Flickr gallery of everyone's fabric designs.
You may have already heard about Spoonflower, but just in case you haven't I wanted to direct your attention to this newish web-forum organization. Talk about giving power to the people!
Have you ever combed the racks of fabric stores searching for a particular print on a fabric and come up dry? So frustrating. Recently I've been on the hunt for baby blue cotton fabric with white polka dots on 100% cotton. You'd think that wouldn't be so hard to find, but I haven't had much success.
Enter Spoonflower. You can submit your fabric print design to them and order a swatch, a fat quarter or up to five yards (they'll increase the maximum in the future) of fabric on 100% cotton that they have printed for you. Shazam! You might want to check their FAQs for more details, and you do have to sign up for an account in order to submit your fabric design for printing. They're still in Beta so you'll be put on a waiting list before you can sign up for an account (I did so last Thursday or something and got my account setup email this morning). I'm trying to figure out what I'd like to have printed on fabric (and what I'd be making with said fabric). In the meantime, I've enjoyed watching their little videos of featured fabrics that they show off before they are shipped to the original designers. There are some really talented folks out there. Check it out!