OK, so the documentation still isn't complete, but I can't wait to introduce my newest concoction - Luz. Luz is a pure-Python implementation of a MIPS-like CPU (as a simulator, of course). This CPU is programmable in an assembly language, a complete assembler for which has been implemented, along with a linker that takes together several object files and creates an executable image to run on the simulator. Oh, and did I mention that it also includes a rudimentary debugger and disassembler? All of this is Luz:

To call Luz new is a bit of a stretch, because I started working on it more than two years ago. It has been a jagged road, with occasional spurts of productivity, but now Luz is finally in a presentable form.

I'll paste from its "getting started guide":

What is Luz useful for? I don't know yet. It's a self-educational project of mine, and I learned a lot by working on it. I suppose that Luz's main value is as an educational tool. Its implementation focuses on simplicity and modularity, and is done in Python, which is a portable and very readable high-level language. Luz can serve as a sample of implementing a complete assembler, a complete linker, a complete CPU simulator. Other such tools exist, but usually not in the clean and self-contained form offered by Luz. In any case, if you've found Luz iseful, I'd love to receive feedback.

This summarizes it, really. Not much more to add, except that Luz is available in source-only form for now, so you'll have to check it out from SVN or just look at the sources in the online browser. Checking the source out is recommended because it allows one to view the documentation in nice HTML format. A few example programs in Luz assembly are available. Luz requires Python 2.6 or higher and the PLY module installed. I tested it on Windows XP and Ubuntu.

I've written an assembler and a CPU simulator before, but that was for a very weird architecture (Knuth's MIX from TAOCP). Luz is a much more useful beast - the CPU is not far from real modern CPUs (the embedded kind, mostly), the assembly language is familiar and best of all, Luz also includes a linker, which will make it much easier to compile C for it in the future.

I'll write more about Luz in sometime later, when I find the time to work on its documentation.