As much as I love the Thursday threads, I think that they are more of an honorable mention, and that pet related threads should rate higher.

One other possibility, even though this brings up bad memories for some, is our handling of the Jessica12345 "death" hoax. It was one of those "people are at their best when things are at their worst" moments. I really felt like a part of a very special cyber community - first in our genuine outpouring of grief, then in our stunned disbelief that someone could do such a cruel thing to us. We healed and became closer after that.