The death of optimizing compilers (PDF), slides by Daniel J. Bernstein.
The Hash Function BLAKE, a book by Jean-Philippe Aumasson, Willi Meier, Raphael C.-W. Phan, and Luca Henzen. Foreword by Daniel J. Bernstein.
Vector quotients: an aid for 3D calculations, by J. H. Condon and M. D. McIlroy.
A notation for the most general form of repetition (PDF, 1984). By Maarten M. Fokkinga.
MAT, the Metadata Anonymisation Toolkit.
git-timemachine, Emacs mode to step through historic versions of git controlled files. Very useful.
dygraphs is a fast, flexible open source JavaScript charting library.