Burdastyle.com user. I make regular use of both the free user-developed and the low-cost company-made patterns. Also, whenever I need to sew something and don't know how, I check Burdastyle.com for tutorials, which have been absolutely invaluable to me on so many occasions.
So, you could say, I am loyal. Except when I'm not. For example: I just downloaded this free pattern for the Lace Ruffle Tunic over at Sew Daily. It's not quite Burdastyle, but I think it's trying to be. And that's OK. There's room enough for numerous open-source sewing websites, in my opinion. Sew Daily so far lacks the fashion bent of Burdastyle. And many of the free project downloads are pretty novice: pillows, bags, drawstring skirts, for eg.
Anyway, I've got my pattern downloaded. I'll be using some white stretch lace I got from my neighbor who was cleaning out her fabric stash, plus leftover peach jersey from this batwing top I made a few months back. I'm all about the peach this spring.