The following ports are available:

6502 6502 CPU and compatible series, especially Commodore 64.
80x86 DOS 80x86 in real mode, the RTOS is loadable from DOS.
80x86 WIN32 enables pico]OS to run on top of MS Windows.
ARM ARM CPU: SAMSUNG S3C2510A (ARM940T core) and compatible series.
AVR MegaAVR: Atmel(tm) RISC core processor.
MyCPU MyCPU: Port for the Homebrew-Computer called 'MyCPU'
PPC PowerPC: IBM PPC440 and compatible w/o floating point.