A selection of
Grothendieck's unpublished mathematical writings
Correspondence  A selection of letters from Grothendieck to
various people
Some of Grothendieck's published
mathematics
Notes of courses given by Grothendieck

Introduction au langage fonctoriel.
Original typed notes, taken by M. Karoubi, of a course
taught by Grothendieck in Algiers in November 1965. 77 pages.

Groupes de BarsottiTate et Cristaux de Dieudonné.
Notes by M. Hakim and J.P. Delale of a lecture course given by
Grothendieck at U. of Montreal in the summer of 1970. 150 pages.

Introduction to Functorial Algebraic Geometry.
Notes written by Federico Gaeta at (the first part of) a 100hour course given by Grothendieck in Buffalo, NY in the summer of 1973. These are not based on prenotes by Grothendieck and to some extent represent Gaeta's personal understanding of what was taught there. 168 pages.
Surveys and overviews of Grothendieck's work
 Rapport au comité Fields sur les travaux de
A. Grothendieck JeanPierre Serre's report on Grothendieck's work for the Fields Medal in 1966

Quelques idées maitresses de l'oeuvre de A. Grothendieck.
P. Deligne’s overview of some fundamental ideas in
Grothendieck’s work.

Notes on the life and work of Alexander Grothendieck.
An 18page biographical article by Piotr Pragacz, originally
published in Polish in Wiadomo´sci Matematyczne 40
(2004).

The rising sea: Grothendieck on simplicity and generality.
A lecture by Colin McLarty.
 The rising tide: Grothendieck
on simplicity and generality. A streaming video of a talk at MSRI by
Colin McLarty on Grothendieck’s approach to mathematics.

A Mad Day's Work: From Grothendieck to Connes and Kontsevitch. The evolution
of concepts of space and symmetry. An article by P. Cartier on
the evolution of the concept of space with emphasis on Grothendieck’s
contributions. Beware of biographical inaccuracies!
 A short review of the GrothendieckSerre Correspondence by John Tate, published in NAW in 2004.

Grothendieck et les motifs (P. Cartier) and Découvrir et
transmettre (A. Herreman) (Notes sur l'histoire et la philosophie des
mathématiques IV), The first entry in this collection of two
independent texts on Grothendieck gives a general and very personal and
readable overview of his contribution and approach to mathematics from
the beginning. The second is not mathematical, but concerns Grothendieck's
relation to the acts of reading, writing, and creation. It is also linked
directly in the section on biographical texts.

Alexander Grothendieck (in Italian)
Alexander Grothendieck:Enthusiasm and Creativity (in English)
An overview of
Grothendieck's mathematical contribution, by Luca Barbieri Viale. The English
article appeared in the book Mathematical lives, SpringerVerlag, 2011.
 Alexandre Grothendieck, magicien des foncteurs  an
article by Luc Illusie.