The MD5 implementation for Common Lisp implemented by Pierre R. Mai a decade ago has been floating around in various tweaked versions for some time now. We have now produced a new consolidated release (release 2.0.0) of this with proper packaging, all known fixes and tweaks and implementation optimizations. The new release is still available from its PMSF page, and its new GitHub home.
Many thanks go to Christophe Rhodes, Alexey Dejneka, Nathan Froyd, Andreas Fuchs, John Desoi, Dmitriy Ivanov, and Kevin M. Rosenberg who improved, tweaked and maintained versions of MD5 over the years.
Note that MD5 has been cryptographically broken, and should therefore not be used in situations where a cryptographically secure hash function is needed. However due to its wide historical use and its remaining suitability in non-cryptographically secure settings, this implementation is still of some interest.