I always have the idea to port a C compiler to target one of my custom CPU projects, but I haven't done it (yet). But I'm always looking at tools to simplify the job.

 One of these is the LLVM (Low Level Virtual Machine) compiler infrastructure. The LLVM itself isn't a compiler -- it helps you build things like compilers. However, the project ships clang , a front end for C, C++, Objective C, and Objective C++. 

 I found it interesting that in a recent blog post , the clang development team claims they, "built all of LLVM and Clang with Clang (over 550k lines of C++ code). The resulting binaries passed all of Clang and LLVM's regression test suites, and the Clang-built Clang could then build all of LLVM and Clang again."

Maybe this will motivate me to get a C compiler done.