Sometimes there are bits in the junk box just crying out the be built into something. In my case I got an old telephone tester that had a Z80 CPU and Z80 DART (Serial) chips. Most of the parts needed to build a small Z80 based computer.... so I did.
The machine is based on this design.... http://searle.hostei.com/grant/cpm/index.html
Grant has done a really excellent job pulling this together, particularly the software and the custom CBIOS for CP/M.
The design is an excellent example of a retro type machine with some modern parts that really reduce the chip count.
In my case I used a 628128 Static RAM (128kb) and only use 64kb, a 128kb Flash ROM chip and only use 4kb and a 64mb Compact Flash card for storage divided into 8mb drives.
No fancy graphics or sound but it runs CP/M really well.
Board before the CF adaptor is fitted
Board after the CF adaptor is fitted
Underside before the CF adaptor is fitting
The wiring is not as bad as it may look in the photos. It is just a case of being methodical and using a multi-meter to check everything you do.
That said... I did need to revert to the Logic Probe and Logic Analyzer at one point to find what turned out to be a solder bridge.