I never met Charles Fillmore, but he had a deep influence on my linguistics education. When I was a graduate student in linguistics at SUNY Buffalo we only half jokingly called it Berkeley East because half the faculty had been trained at Berkeley and the department had a *perspective* on linguistics that was undeniably colored by Berkeley theory. Charles Fillmore was a hero at SUNY Buffalo and it was hard to take a class that didn't reference his work. His work on constructions and frame semantics was the underpinning of my interest in verb classes and prepositions.
I can't offer any unique thoughts on the man, so I'll simply point to some folks around the web who have offered theirs:
A Roundup of Reactions
Paul Kay - Charles J. Fillmore
The magnitude of Fillmore’s contributions to linguistics can hardly be exaggerated.
George Lakoff - He Figured Out How Framing Works
He discovered that we think, largely unconsciously, in terms of conceptual frames — mental structures that organize our thought. Further, he found that every word is mentally defined in terms of frame structures.
Dominik Lukes - Linguistics According to Fillmore
Charles J Fillmore who was a towering figure among linguists without writing a single book. In my mind, he changed the face of linguistics three times with just three articles (one of them co-authored).
UC Berkeley - Linguistics Department
He was a gifted teacher, a beloved mentor, a treasured colleague and friend, and one of the great linguists of the last half-century.
Arnold Zwicky - Chuck Fillmore
...with a link to a wonderful video he made about his career in 2012.