I would say Emacs with SBCL is a good start. I haven't started PAIP yet, I'm working through the Touretzky Lisp book, "Common Lisp: A Gentle Introduction to Sym

I would say Emacs with SBCL is a good start. I haven't started PAIP yet, I'm working through the Touretzky Lisp book, "Common Lisp: A Gentle Introduction to Symbolic Computation" as a warmup before starting PAIP. I've found that Inferior Lisp mode in Emacs is sufficient for working through those examples. It seems like a lot of working programmers are using SLIME with Emacs though.