I would second learning Clojure. Functional programming has taken on an approach to concurrency that common lisp just never had and never will. Clojure is a more modern, usable lisp dialect that deals with concurrency. You will learn all the same lessons that lisp can teach in clojure plus a lot more with modern tools. Its just not worth learning common lisp as the first lisp today.
i7 3930k @4.4, 2xMSI GTX 680, 16GB Corsair 2133 RAM, Crucial m4 500GB, Soundblaster Z
Custom watercooled by 2x MCR 320 and 1 MCR 480
Zowie Evo CL EC2, Corsair K70, Benq XL2411T