WindowMaker. Back again to wmaker, because of some annoying bugs in blackbox when resizing emacs frames. In addition, the new wmaker version 0.8 let's you launch already docked apps from the command line (or a script, for that matter), a functionality i really missed. And, finally, i took a look at the bb sourcecode, and found it very low quality C++, so... let's see how long i stick to wmaker this time!
MMDK. Must have a look at Knuth's implementation of MMIX before starting my own: it seems quite powerful, and maybe it's no use reinventing the wheel; there is even a gcc port cross-compiling C/C++ to the MMIX emulator!