I'm the principal author of GMP, the GNU multiple precision arithmetic library. GMP development is fun, since it combines maths with low-level programming. I earlier wrote GNU cp, split, and a couple of other command-line utilities, as well as the GNU superoptimizer. And I wrote the foundation and first implementations of GNU libc's memcpy, memmove, and associated functions. I am a long-term contributor to the GCC project, but now I only rarely contribute patches, and I stepped down from the GCC Steering Committee in early 2004.

Publications:

Branch elimination and the GNU superoptimizer (PLDI'92)
Integer division by constants (PLDI'94)
How We Cracked the Code Book Ciphers (2000)
GMP - a functional foundation for fast arithmetic
Instruction latencies and throughput for AMD and Intel x86 processors (April 2017)
Improved Division by Invariant Integers (IEEE Transactions on Computers, 11 Jun. 2010)
Division of Integers Large and Small (August 2009, to appear)
Defeating modexp side-channel attacks with data-independent execution traces (rejected from Eurocrypt'13)

Misc links:

Integer factoring
Spam from ACM
Adaptec makes fun of its customers
Running Xen efficiently
Qemu--a multi-arch virtualiser
Status of BSD guests atop KVM and Xen
Torbjörns tankar om valfrihet (Swedish)