I suppose the original poster could clarify whether they were interested primarily in examples of the Scheme-derivative language "Racket" being used in production, or in the system/VM/runtime "Racket" being used in production. Since Racket (the system) now makes it very easy to define new languages on top of it with the #lang keyword, it might be nice to get more clearly distinct terms for these. The way the Java world uses JVM vs. Java, e.g. you'd say that a Clojure app runs "on the JVM", but it's not in Java.
Arc is not Racket.