See http://koo.corpus.cam.ac.uk/projects/th ... uters.html for 3 (or 4) impressive homebrew systems by DJ Greaves.
Starting in 1977 with "CHAOS", a ROMless front-panel based design using the Signetics 2650, which develops into a 32k dual-floppy system with keyboard and video (and, intriguingly, a "Numeric Coprocessor") and is then rebuilt in 1983 as a system with a 20MByte hard drive, a second 2650 to drive an intelligent terminal and also an 8088 with 64k RAM for "more serious application programs". Software includes a port of WADUZITDO and a "simple PASCAL compiler"
Then in 1986 we see a 68k machine, programmed in BCPL and running Tripos, and then in 1991 a 4MByte 68030 machine: "The operating system was written in C using a C compiler that had been bootstapped with the BCPL compiler running on Stallone. It provided virtual memory with demand paging and was posix-like in most ways. It was basically a homebrew linux running on homebrew hardware."
These days David seems to be a lecturer in VLSI and building CPUs in verilog: http://technotes-djg.blogspot.co.uk/