I tend to enjoy Scheme more than Common Lisp for just hacking around, but I'm by no means an expert Lisp hacker. If you decide to check out Scheme though, Chick

I tend to enjoy Scheme more than Common Lisp for just hacking around, but I'm by no means an expert Lisp hacker. If you decide to check out Scheme though, Chicken Scheme has been awesome for me. It's very fast, compiles to C, had a ton of great "eggs" (modules / packages), and seems to have a somewhat friendly community with decent documentation.