Since a lot of people ask what kind of interfacing I use I thought a quick post was in order. To answer the question I use Form Flex All-Purpose for almost everything. It is a fusible woven interfacing and doesn't melt and get all wrinkly like the non-woven interfacing. It is designed for medium weight fabrics but I find it works well even on lighter weight cotton fabrics.
It comes in black and white. The black doesn't seem to adhere quite as well and sometimes comes up off the fabric in places, but it still works fine and it is wonderful to have the darker color when using dark fabrics. I recommend giving it the max fuse time (10 seconds each press) and let it sit and totally cool off before picking it up.