Their continuation-based web server is neat, if you can handle not complaining about the same thing in the Arc/HN combination everyone does when it is brought up.

http://docs.racket-lang.org/web-server/

I also recently discovered a web sockets library, but am not good enough at coding Racket to use either yet. I am definitely planning on it.

(And seeing you're handle, just want to thank you for your contributions to Clojure; I can only image what would happen if you got more involved in the Racket community).