Racket is a programming language. Racket is the language implementation formerly known as PLT Scheme. Racket is available now. To quote the release announcement:
With Racket, you can script command shells and web servers; you can
quickly prototype animations and complex GUIs; regexps and threads
are here to serve you. To organize your systems, you can mix and
match classes, modules or components. Best of all, you start
without writing down types. If you later wish to turn your script
into a program, equip your Racket modules with explicit type
declarations as you wish. And Racket doesn't just come as a typed
variant; you can also write your modules in a purely functional and
Racket comes in so many flavors because Racket is much more than a
standard scripting language or a plain programming language. Racket
supports language extensibility to an unequaled degree. A Racket
programmer knows that making up a new language is as easy as writing
a new library.
If you haven't looked at, say, Typed Racket, Dr Racket, or how to create your own languages in Racket, now might be a good time.