An outstanding collection of articles is available in the January 2013 issue of the Notices of the AMS:
(in case the link will not function,here is a pdf: rnoti-p24).
A true mathematician, not as mathematicians usually are these days, but as they should strive to be. Here is a quote about his legendary seminar (taken from page 26 of the linked paper):
“My seminar is for high school students, decent undergraduates, bright graduates, and outstanding professors.”
In his article, I.M. Singer compares him to Cezanne and Matisse. Is this becoming a fashion? See Cezanne and Perelman.
I would not compare him with Cezanne, though. Cezanne was a reclusive, throwing his paintings as Perelman put his papers on the arXiv, … My suggestion is to compare Gelfand with Leonardo da Vinci, because he really was a Renaissance Man.