The DX-Designs P112 is a single-board computer built around the Zilog Z80182 processor chip. Running typically at 16MHz and addressing up to 1MB of RAM, the P112 makes an excellent microcontroller board and development system. In addition, it has a 32KB flash ROM, real-time clock with battery backup, serial and parallel ports and floppy-disk interface. The board can run a variety of operating systems, including CP/M, MP/M and a number of real-time OSes.
On this site you will find a number of software packages, including operating system ports, bootable floppy disk images, patches and modifications to the standard supplied software I've done over the years.