Unpublished Mathematical Texts
Eighteen thousand pages
of Grothendieck's personal mathematical writings, left behind when he
abandoned Les Aumettes for Lasserre in 1991, were scanned by the University of
Montpellier and are available online.
Esquisse Thématique  an overview that Grothendieck wrote of his own work, with an English version (courtesy of
G. Aiello).
En Guise de Programme, Page 1 and Page 2  a text
written by Grothendieck as a course description while teaching in Montpellier.

Espaces Vectoriels Topologiques
 These are the origial French course notes from Grothendieck's
series of lectures in São Paulo in 1954!

A General Theory of Fibre Spaces with Structure Sheaf
 This early paper, written while Grothendieck was at the University of
Kansas on an NSF grant in 1955, was only published as an NSF research report.

Motifs  Apart from some letters to Serre and others,
this preliminary text dating from 19651970 and handwritten (typed up by
later readers) is the only mathematical text that Grothendieck
can be said to have written on the subject of motives, outside of some
letters to Serre (GrothendieckSerre Correspondence).

Tannakian notes  A 25page text (undated  1960's?) from J. Milne's files, on Tannakian categories over
a field and the toolbox of liens, gerbes etc. It contains a discussion
of applications to isocrystals and DieudonnéManin theory.

Notes of Grothendieck's last lecture, at the IHES in 1975, typed up in
2003.

La Longue Marche à travers la
théorie de Galois, Contents  Table of contents.
This manuscript, consisting of some nearly 800 handwritten double pages, dating
from 1981, was left behind with Grothendieck's other unpublished manuscripts
when he disappeared in 1991. Typed in Tex, it comes out to about 400 pages. It goes together
with a further 1000 pages or so of additional notes and sections which have not
yet been read or typed. Many of the major themes were summarised in the
1983 manuscript Esquisse d'un Programme linked below.

La Longue Marche, Part Ia  La longue Marche
à travers la théorie de Galois, (sections 125)
Not yet available.

La Longue Marche, Part Ib  La longue Marche
à travers la théorie de Galois, (sections 2637, 110 typed pages)

La Longue Marche, Part II 
Part II of the Longue Marche (sections 3853) has not yet been typed yet, except
for the very long section 49 (129 typed pages).
Section 49

Esquisse d'un Programme or
Sketch of a Programme
 Grothendieck's 1983 research project, included in his application for
a transfer from the university to a research position in the CNRS for the
remainder of his career before retirement. This text was later translated into
English and published in Geometric Galois Actions vol. I,
LMS Lecture Notes 242.
 Pursuing Stacks
 Georges Maltsiniotis's page, for a scan of the 500 page 1983 text by
Grothendieck and further information about it. For some information
on how Pursuing Stacks came to be written, see the article by
Ronnie
Brown.
 Les Dérivateurs
Grothendieck's 1991 manuscript `Les dérivateurs'.

Scans of Grothendieck's prenotes for EGA 5 (171 pages)
The prenotes were given to Piotr Blass by Grothendieck in 1987. The
pages are somewhat mixed up so start by consulting the
Table of Contents. See also the 1987 letter from Grothendieck to
P. Blass in the list of letters below. Links to the version of this
part of EGA typed, revised and published by P. Blass and S. Klasa
can be found on the published mathematical texts page.