Sharon Sews Sixth Scale Stuff. Try saying that swiftly seven times.
Found a sewing blog that has tutorials for Barbie stuff. Whoo hoo! Here is the link to Sharon Sews post about sewing for Barbie-sized dolls. Hope you find the tips useful.
There are tips for people scale fashions, too, as well as other crafts. Me, I am mostly about the playscale stuff. If I can adapt the other tips to that scale, great. If not, shrug.