History:

 The project began on 10/11/2013 and I had an acceptable working 1.0 version on 11/22/2013

 Here's another example of a project that came into being simply because we had some parts that "might" make it work.  Having completed my EPROM programmer a few days before, I started wiring the board on 4pm Friday afternoon and had it blinking an LED at 2:30pm the next day after correcting only about 4 or 5 wiring errors.
By 10/13 I had a working serial interface running at 1200 baud which later was increased to 9600.

Resources and Tools:

Thankfully the Z80 was quite a popular CPU used in early TANDY computers, TI calculators and the 1st Nintendo Game Boy.
This made finding resources online easy. (see  http://www.z80.info )

I found Thomas N. Anderson's TASM assembler worked quite well.  Once a reliable serial interface was developed I could work within a Z80 Emulator ZEMU - Z80 Emulator by Joe Moore.  This freed me from needing to burn an EPROM with each code iteration. 

Once the HEX file upload feature was working I could also use SDCC 
(see http://sourceforge.net/apps/trac/sdcc) to compile  C source code that could be uploaded and run on the system.

6/2023 Update
Added a hardwired LED and speaker to this board (see updated schematic link below) and updated the monitor software to support them. Now there's a spiffy red LED that blinks every second while the system is waiting for input and a short beep is emitted from the speaker after reset.
Routines for blinking and beeping the new hardware are in the updated ROM code.
Also added a LINUX versions of the .hex file transfer utility.
For assembling Z80 code on my linux box I'm using zasm from:  https://k1.spdns.de/Develop/Projects/zasm/Distributions/

Since TASM won't run on Windows 10 I'm now using zmac  from: http://48k.ca/zmac.html 

Software:
The current code takes up about 16k of the ROM space which include the BASIC interpreter.

Dump 256 function

List function

Assemble, and Go  functions