Anarki: a publicly modifiable fork of PG's and RTM's Arc Lisp (http://www.paulgraham.com/arc.html)
To run, install Racket from http://racket-lang.org, then:
$ git clone http://github.com/nex3/arc
$ cd arc
$ ./arc.sh
arc> :a
$
If you run into trouble: http://sites.google.com/site/arclanguagewiki; http://arclanguage.org/forum
To run the HN server: lib/how-to-run-news