I just joined the group purchasing a cones of Superior Thread's King Tut on Massdrop and thought I'd mention it here for those that may not yet have discovered this source.
And then I found what could be the perfect border/backing fabric for the scrappy Briar Patch quilt I blogged about yesterday–a wide black and white backing fabric by Windham covered with color names ... and decided I needed that, too.
It seems a perfect match for Rainbow Scraps projects.
On Massdrop, you can vote in polls about what you'd like to see offered and join group purchases with prices that drop as more buyers opt in. In the past, I have purchased fat quarter bundles and Quilter's Dream wool batting (which is now being offered again, if you're interested) and some non-quilty things ... though I confess it is the quilting category items that tend to grab my attention.
I am not associated in any way (except as a happy customer), but do think it's a great concept and an interesting site worth checking out.