Twenty Random Facts about Remus and Sirius, by minnow_53. From what I can tell, this is the first story in this style.
thislerose was inspired, and wrote Twenty Random Facts about Lily and James.
The following two are actually two halves of the same story--"Twenty Random Facts about the Eldest Weasley Boys"--a genfic written by sheafrotherdon and devkel, respectively.
Part One: Ten Random Facts about Charlie Weasley, by his Older, Smarter, and Much More Handsome Brother, Bill.
Part Two: 10 Random Facts About Bill Weasley, As Told By Charlie Weasley, His Ridiculously Handsome, Intelligent and Thrice-Voted-Britain's-Sexiest-Dragon-Ke
Read them all.
(x-posted to my journal)