Never heard of it, and the only thing I can think of is self-explanatory (i.e., you take some stuff, and rank it).

I assume it's just the ranking of stuff.

Yeah.. someone lists 3 things, you rank them, then leave 3 things for someone else to rank. They can be fun to insert in other threads as an afterthought but can lose steam as a standalone thread.

'The Kenny' (a variation created by some friend of a friend named Kenny) kind of killed off the original rank, where someone lists something and you name one thing slightly better and one thing slightly worse. There's a Kenny thread a few posts below. I don't quite have the creative writing chops to do it justice but they're sure fun to read.