If you prefer a small-language, build-up-blocks version of Lisp, Scheme may be a better place to start than Common Lisp (clisp is a Common Lisp implementation). There are other pros/cons, but in general Scheme is the more minimalist branch of the Lisp family tree. Racket (http://racket-lang.org/), formerly "PLT Scheme", is one popular choice in the Scheme family. Clojure (http://clojure.org/) is another possibility, neither Scheme nor CL, that has recently been gaining popularity.