I interface everything, so I go through a lot of interfacing and I try to only buy it when it’s on sale. My favorite is Pellon SF 101. I also use Pellon 50 sew-in and Pellon 926 sew-in.
These sales happen a few times a year and this is usually when I stock up.
Jo-Ann Fabrics has interfacing 40% off this weekend (August 3-5) and then a 25% off coupon. If you didn’t get a flyer, you can print the coupon here.
At my Jo-Ann, SF 101 is $5.29, so with the discount and coupon it ends up being $2.38 a yard. The nice thing with these sales is that you don’t need to have a coupon for every different cut. I usually can find a 40% or 50% coupon to use, but if I need three different kinds of interfacing that doesn’t work as well. So go, stock up while it’s cheap! Then go buy some nice fabric from your local quilt shop. :D