A couple of Round Robins is the closest I've come.
They were fun but also challenging. I was a new quilter so I learned a lot about doing the math for multiple pieced borders as well as choosing and working with fabrics that were not my personal taste. I was glad I participated but it only worked because the group (it was a small guild) decided from the beginning that it was purely for fun and not to expect masterpieces. It also really helped that each person included a list of what styles/colours/etc she really liked and what she absolutely hated and we all respected each other's preferences. I think the beginners had more fun than the experienced quilters, though.
I haven't been part of a guild for years yet I often think about finding one or two like-minded gals for an informal group to quilt or embroider along side each other, mainly for social company but also for encouragement and critique.