Maz Spork released the Z80 ASM source[0] of Buggy Boy[1] for 128K Spectrum, though it since disappeard from his site.

More of this type of thing!

[0] http://web.archive.org/web/20030629124143/http://maz.spork.d...

[1] http://www.worldofspectrum.org/infoseekid.cgi?id=0000746