Paper Tape Images of Eliza in BBN PDP-1 Lisp
github.comRuns in CLISP and presumably other modern Common Lisps, using the Lisp source in the parent directory.
In Emacs,
M-x doctor
And while it seems to be broken in the copies of EMACS I just tried (stock GNU EMACS on Debian squeeze and wheezy), M-x psychoanalyze-pinhead is supposed to feed it Zippy the Pinhead quotes (right now it only feeds it one stock quote about cabbage).
A lot more fun was when a professor in a class I was taking in 1978 logged into a Stanford computer, and connected PARRY, a serious attempt at simulating a paranoid schizophrenic (http://en.wikipedia.org/wiki/PARRY), to Eliza.
Ah, reading the Wikipedia entry I see this is a famous enough concept to have been immortalized in an RFC by Vince Cerf: https://tools.ietf.org/html/rfc439
Sadly legal concerns in Emacs 22 resulted in the Zippy quotations being replaced with the cabbage quote: https://en.wikipedia.org/wiki/Zippy_the_Pinhead#Appearances_...
Yep, eliza is still useful, especially if your day job involves a lot of C++ code :)
Absolute classic. The transcript of one such discussion gets quite amusing near the end. :)