Lisp500: A feature-packed Lisp in 500 Lines of C (plus a file)

This was written in the early 2000's.

Make no mistake: this is not one of those "I hacked a Lisp in C to learn about both languages".

It has a garbage collector, conditions (with restarts), a package system, macros (including local ones: macrolet, symbol-macrolet), stream, hash tables, structures, ... and even a compiler.

It has probably not been posted to HackerNews before, because the author's original site for this had been inaccessible for years, and the project fell into obscurity.

There are some derivatives like Lisp800 and Lisp5000 the latter of which tries to de-obfuscated the original.