4Clojure is a site which offers 156 exercises to learn Clojure by solving some sort of programming challenge. The exercises are grouped from Elementary, Easy, Medium to Hard. For each you are presented with an explanation and a set of test cases which when run with your entered function must pass.
I decided to mention 4Clojure today because I've gotten back to it and am trying to finish the last few problems. I can say at this point the Hard problems are in fact Hard.
I highly recommend trying to get through as many of the 4Clojure exercises as you can if you are an aspiring Clojurist.