Racket is a full-spectrum programming language. It goes beyond Lisp and Scheme with dialects that support objects, types, laziness, and more. Racket enables programmers to link components written in different dialects, and it empowers programmers to create new, project-specific dialects. Racket's libraries support applications from web servers and databases to GUIs and charts.
The offical, comprehensive and very well-written documentation can be found at [http://docs.racket-lang.org/]. On this site (Stack Overflow Documentation) you can find user-contributed examples.
Go to http://racket-lang.org and click the download button.