#lang racket
(provide hello)
(define (hello [name "World"])
(string-append "Hello, " name "!"))"Racket (formerly named PLT Scheme) is a general purpose, multi-paradigm programming language in the Lisp/Scheme family. One of its design goals is to serve as a platform for language creation, design, and implementation. The language is used in a variety of contexts such as scripting, general-purpose programming, computer science education, and research." - Wikipedia
You can learn the basics of Racket through a coule of books. Start by checking out How to Design Programs or the slightly less formal but enjoyable Realm of Racket.
The official language website can be found at http://racket-lang.org/ and the source code is at https://github.com/racket/racket/. You can find the community on twitter, email or slack.
Join the Racket track
Exercism is a great website where I was able to have some very interesting challenges.
Once you join the Racket language track, you will receive support and feedback from our team of mentors. Here are the bios of a few of the mentors of this track.
These are a few of the 28 exercises on the Racket track. You can see all the exercises here.