I'll second PCL. It really is incredibly good. Unlike some other introductions to Lisp, which tend to be of the algorithmic, CS side of things, PCL approaches

I'll second PCL. It really is incredibly good. Unlike some other introductions to Lisp, which tend to be of the algorithmic, CS side of things, PCL approaches things from more of a scripting/software-development side. Common Lisp really is a great developer's language, and PCL helps show why. Peter Seibel's a great writer, too.