I had years of programming experience before I learned Common Lisp—or any Lisp, for that matter—and I’ve always regretted it. Lisp teaches you new ways of thinking about programming and every programmer should be familiar with it even if they never use it in a non-trivial way. Emacs users have an advantage here because it’s almost impossible to use Emacs without learning at least a little Lisp.
The problem is that it’s hard to get started. Lisp is the second oldest (non-assembler) programming language and some of the terms it uses have different meanings now. Steve Losh has performed a public service by publishing A Road to Common Lisp, a longish post on how to get started with Common Lisp. He doesn’t teach you the language or how to program in Lisp; he focuses on the steps you should take and the resources you should use to learn Lisp and to set up a reasonable Lisp programming environment.
His first piece of sage advice is not to worry about an editor. Use whatever editor you’re familiar and comfortable with. Later, when you get more experienced, he says you’re going to have to choose between Vim and Emacs because of their Slime or Slime-like plugins. He’s a Vim user himself so this is more than a roundabout piece of Emacs evangelism.
He goes on to suggest some useful books and explain some of the harder concepts like “packages,” “systems,” and “projects.” Finally, he discusses some of the popular libraries that perform tasks not built into the language itself. It’s a great post and should be very useful to n00bs. I wish I’d had it when I was learning Lisp.