I'm currently learning Clojure and ANTLR (separately), that being the case, this Clojure ANTLR grammar's good study material. This grammar comes from the counterclockwise eclipse plugin for Clojure.

The following video is of language designer Rich Hickey giving a brief overview of the Clojure language, and highlighting its approach to non-painful concurrency. Hickey's a fascinating and concise speaker, who really gets into the meat of the concurrency problems in application programming today, showing how Clojure was designed from the ground up to simplify the process of concurrent programming.

So, I'm on the road towards learning Clojure, via Stuart Halloway's Programming Clojure. It's an OK book, hardly the gem (no pun intended) that the pickaxe was. However, it is thorough, and is less disjointed than simply googling around for Clojure info and docs.

With all that in mind, Casting SPELs in Clojure is a welcome companion to Halloway's book (perhaps best as an introduction). While not nearly as comprehensive, it's more readable, and has a more fluid style. After I get through the basics of Clojure, I'm looking forward to finally learning about Monads in Clojure.