Lisp is one of the oldest programming languages still in
use today—Fortran is older by a year, but the Lisp community (or
communities) seems to be the more dynamic of the two. In any case, the Lisp
landscape has a lot of nooks and crannies to explore; I recently ran into a
dialect that I had not encountered before: Racket. That may simply reflect
ignorance on my part, but, while I was introduced to Lisp (too) many moons
ago, I had not really paid it much mind until I sat in on a talk about Lisp at linux.conf.au earlier this
year. Something about Racket caught my eye, so I did some poking around to
see what it is all about.

Source: LWN.net – [$] Racket: Lisp for learning