Agnix is a small, educational operating system kernel for i386, supporting 32-bit protected memory mode, paging, hardware switched tasks, memory tests, PCI bus, devices, PCI IRQ routing, RT timers, network protocols. It is available with all the source code and is fully compatible with the Linux kernel API.
rtldi is an ELF program interpreter that makes it possible for executables to use their own ld-linux.so.2 and libc.so.6 and associated shared libraries, independent of the default versions installed in /lib and any other executable. It facilitates the simultaneous interoperation of programs that were originally linked using different generations of glibc6. In theory it should not be necessary, but in practice glibc6 has not always been backward compatible.
CUT is a unit-testing framework for C, C++, and Objective-C. Unlike other unit testing tools, CUT doesn't strive to be an SUnit clone. It automates a lot of the drudge work often encountered when using other unit testing packages for the C family of programming languages. CUT may also be used to unit-test assembly language software in some circumstances.
Fenris is a multipurpose tracer, debugger, and code analysis tool that detects and documents high-level language constructions, can recover symbols, graph program execution flow, detect internal functions, recover symbol tables, and deal with anti-debugging protection. It features a command-line interface as well as a SoftICE-alike GUI and Web frontend.