This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
Especially if you are familiar with the JVM, then I think Clojure is an excellent first Lisp.
If you'd like to stray into other flavours, then Racket is an excellent choice (and Dr. Racket is an excellent dev environment). Alternatively, Gambit Scheme might be attractive insofar as clojure-scheme compiles down to Gambit (and thereby to C). I don't think learning these will help you learn Clojure; but, they do do certain things differently that will nevertheless be useful to you in helping you think through various kinds of problems.