I learned Lisp in the late 80's. First was muLisp. Later was pleasantly surprised when AutoCad used Betz's XLisp as their embedded language. After a decade or so I returned to Lisp as a mind exercise. I believe like Paul Graham that Lisp forces more attention to design up-front than most other languages which I take to be good exercise for all languages. Currently I'm using newLisp and having a blast. Haven't gotten around to Haskel yet, but I will. I've figured out that at least for me, a working knowledge and ability in Perl, Lisp, Python, Ruby and Haskel seems to be mandatory. When lisping, my sig is:
"Censeo Toto nos in Kansa esse decisse."—D. Gale "ℑ♥λ"—Toto
"Never try to teach a pig to sing...it wastes your time and it annoys the pig."