Wilferg on this site just recently turned me on to Urban Threads - if you're looking for stuff that's a little off-beat that's a GREAT site for embroidery designs. Very reasonably priced, too. I've bought a set of designs I intend to use for a Christmas gift for my sister, but I haven't stitched them out yet. Plus more that I just liked, for myself.
I've also bought from EmbroideryDesigns.com - they're a little expensive, it seems to me, but they have tons of designs and so far the ones I've used have stitched out nicely. They also have free embroidery designs you can download.