Anything related to the karger thompson attack: proof of concept demos, mitigations, theory.
- multics the original paper explaining the attack (before thompson!)
- SCM Security by Wheeler (Secure distribution & compilation of source fundamentals; Karger advised mastering it)
- rotten by rntz (thompson attack demo)
- rust infection by manishearth (thompson attack demo in the rust compiler)
- tcc ACSAC by daved wheeler
- CompCert by Leroy et al (Mathematically-verified, C compiler whose specs and proofs checked with tiny, verified checker)
- CakeML by Myreen et al (Mathematically-verified, SML compiler whose specs and proofs checked with different, tiny, verified checker)
- VLISP by Oliva and Wand (Article has links to VLISP which mathematically verified PreScheme and Scheme48)
- KCC by Rosu et al (Executable, formal semantics for C in rewrite logic; could do that w/ simpler engine)
- TALC by Cornell (Typed, assembly language to verify safety w/out compiler; checker can be simple; C subset + verified compiler to TALC)
- CoqASM by Microsoft Research (Bootstrap in verifiably-safe assembly in prover checked by tiny, verified checker)
These are tools written in ubiquitous languages, therefore they can be used in a wide variety of contexts.
- shasm by Hohensee (x86 assembler written in BASH)
- AWKLisp by Bacon (LISP written in Awk; includes Perl version from Perl Avenger)
- Gherkin by Dipert (LISP written in Bash)
- BASH Infinity by Brzoska (BASH framework/routines that might help write compilers in it)
- mal "make a lisp" implementing a very basic lisp interpreter in hundreds of languages
-  A new bootstrapping project that is built up to a self host language above assembly from a minimal DOS platform.
Small C Compilers
- c4 by rswier (incredibly short c compiler)
- cc500 by edmund grimley-evans (tiny c compiler)
- CUCU by Zaitsev (Small, C compiler designed for easy understanding)
- SmallerC by Frunze (Small, single-pass, C compiler for several ISA's)
- picoc interpreter.
- C Interpreter by Dr Dobbs (Describes building a C interpreter with source)
-  Small C for I386 (IA-32)
- Selfie, a tiny self-compiling compiler for a subset of C, a tiny self-executing MIPS emulator, and a tiny self-hosting MIPS hypervisor, all in a single 7kLoC file. HN discussion. Paper.
- Tiny C expression compiler Written in Forth based on tinyc.c by marc feeley.
-   C compilers by Rui Ueyama blog
-  10 hour self hosting c compiler
Grammars, Parsing, and Term Rewriting
- Grammar Executing Machine by McKeeman and He (Incrementally extend languages from simple to complex grammars in interpreter(s))
- peg by kragen (parsing)
- PEG-based simple compiler by Ian Piumarta
- META II by Bayfront Tech (Original meta-compiler w/ live code and detailed tutorial; OMeta was successor)
- META II implementation by Lugon (Looks like a small implementation of META II; also bootstrapped in META II)
- OMeta# Intro by Moser (OMeta intro that nicely illustrates the meta approach/advantages)
Virtual Machines, Instruction Sets
- P-code by Wirth (High-level language & libraries target ultra-simple, portable interpreter)
- sweet16 by Steve Wozniak
- Tiny BASIC by Allison (Small BASIC whose original VM took 120, virtual opcodes to implement using 3KB RAM)
- Klip by Cutting (Compiler & runtime for simple language for students; done in C#; runtime is very readable)
- Uxn by Linvega (Portable VM with 32 mnemonics implemented in 100 lines of C89; self-hosted assembler)
CPU's for Bootstrapping: The Simple, The Verified, and The Necessarily Complex
- NAND2Tetris by Nisan and Schocken (Guide that teaches hardware step-by-step in fun way with simple CPU emerging)
- J1 by by Bowman (16-bit Forth CPU in 200 lines of Verilog that does 100MIPS on FPGA's)
- H2 by Howe (Modified, VHDL version of J1 with detailed description and Howe's code MIT-licensed)
- RISC-0 by Wirth (Simple, RISC CPU & SOC designed for Oberon language with detailed docs and source online)
- JOP by Shoeberl et al (Embedded Java processor that takes up 1830 slices on FPGA)
- Scheme Machine by Burger (Scheme interpreter implemented as CPU using formal methods)
- ZPU by Zylin AS (Tiny, 32-bit CPU for deep embedded apps in 440 LUT's)
- J2 by Landley et al (Clone of cost-efficient, SuperH-2 CPU in open-source)
- VAMP by Beyer et al (Formally-verified, DLX-style processor in 18,000 slices on Xilinx)
- Leon3 by Gaisler (Industry-grade, 32-bit SPARC w/ auto-configuration of core and GPL license)
- Rocket by Univ of CA (1.4GHz RISC-V CPU and generator for customization)
- OpenPITON by Princeton (25-core, shared-memory, SPARC CPU open-sourced and very scalable)
Minimal Operating Systems
- KolibriOS - lightweight assembly OS.
- MikeOS - same.
- Sortix - modern reimplementation of POSIX in C. (Note: No perl port and GCC does not build natively on it. (yet.))
- ASMLINUX - linux kernel, but the userspace is implemented entirely in assembly.
- LFS - Guide on building Linux and the GNU userspace.
- NetBSD build.sh - Cross-build a complete NetBSD ISO from a foreign OS. There's also a guide in the official NetBSD docs.
- lh-bootstrap - alternative linux distro, using musl instead of glibc.
- xv6 - UNIX teaching OS MIT
- OS/161 - UNIX teaching OS Harvard
- https://landley.net/toybox/about.html - Toybox, alternative to Busybox by Robert Landley, see also Aboriginal Linux and mkroot by the same author, which are all geared toward a minimal boostrappable system
- https://github.com/pikhq/bootstrap-linux - Another take at a bootstrappable Linux system
- Project Oberon - Operating system and programming language Oberon (from the creator of Pascal - Niklaus Wirth)
- TinyGo Operating system in programming language Go
- TamaGo - Another operating system in programming language Go
- seL4 Microkernel - OS kernel in less than 10.000 lines of source code and less than 150 KB binary
- Ultibo - Unikernel for Raspberry Pi written in FreePascal
- https://ds9a.nl/amazing-dna/#bootstrapping - DNA seen through the eyes of a coder