Here is the comment I shared on one of those posts:
I met him once when I was a grad student at Cornell. Besides seeing him give a talk (I think I saw him speak on two other occasions as well), we had a "round table" with him and students, and it was great to get a chance to pick his brain. One major point of discussion concerned people with physics training (and, for some in the room, who would get PhDs from the physics department) applying methods and tools from physics to problems that were not physics. It was a discussion about identity crises.
(Tip of the cap to Sara Solla.)
Update: Predrag Cvitanovic posted a really cool picture from Kadanoff's 75th birthday conference.
Update (10/28/15): The American Physical Society has now posted an obituary.
Update (11/02/15): The New York Times has now also posted an obituary. The article starts with "Leo P. Kadanoff, a physicist who provided critical insights...", and of course "critical" was absolutely the right word to use here. (Tip of the cap to Ernie Barreto.)
Update (12/01/15): Nigel Goldenfeld published an obituary for Kadanoff in Nature Physics. (Tip of the cap to Sang Hoon Lee for pointing me to this article.)