Or at least it's the first one known to us. From Pachacutec (Huffington Post), blogging last month about the examination of potential jurors in the Libby trial, and quoting "one of the day's last potential jurors[,] a young defense attorney from one of the law firms in town":

He cites first among the blogs he read "Glenn Reynolds, Instapundit" before throwing in Josh Marshall's Talking Points Memo, DailyKos, Eugene Volokh, How Appealing and some other law related blog....