A complete compiler toolchain that will cross-compile ANSI C, K&R C, Pascal, Modula-2, Occam, Fortran and Basic for a number of architecture including, but not limited to, the 6500, 68000, Z80, i80, i86, i386 and PDP-11.
Simple. Useful. Light.
The ACK may be one of the best compilers ever. It's a great project to restart it for a mature operating system. http://fruttenboel.verhoeven272.nl/ack/index.html
I cannot find the Amsterdam Compiler Kit's manual.