Installing Clojure is pretty easy (http://clojure.org/getting_started) and you can get far with the REPL. After you've played around a bit, you will probably starting using lein (like maven/ant, but for Clojure), which handles REPL startup, dependency management, JAR building, etc.

For IDEs, I really like IntelliJ + the La Clojure plugin. Many of my coworkers us Emacs + Swank/SLIME. I'm not an emacs user and don't know much about that setup, but it's a very popular setup.

A book that I liked a lot is Clojure in Action (http://www.amazon.com/Clojure-Action-Amit-Rathore/dp/1935182...). I've also heard that The Joy of Clojure is excellent, but it's more appropriate after you're already comfortable with Clojure.

As for online resources, I've found https://github.com/functional-koans/clojure-koans to be very useful. You can clone the project, which consists of a lot of "fill-in-the-blank" unit tests. The tests are designed to teach you the common functions and data structures available in Clojure.

> Do you seriously expect me or any other serious programmer in a business environment sorting a million integers in a million different ways?

Well my apologies for not immediately understanding your specific situation... I can assure you I meant it as a kind suggestion.

Perhaps you could look at Clojure In Action[1]? It's supposed to be a pragmatic introduction for people with some existing programming experience. From the Amazon page, "is a hands-on tutorial for the working programmer who has written code in a language like Java or Ruby, but has no prior experience with Lisp."

[1] http://www.amazon.com/Clojure-Action-Amit-Rathore/dp/1935182...