What Lisp should I learn?

I already know Scheme (read SICP, took the class, got an A, wrote a logo interpreter in Scheme, wrote a Scheme interpreter in Python, etc.) but I haven't touched it much in two years. It seems to be great for computation, and I can certainly see where it would be a perfect fit for artificial intelligence, but I can't imagine using it for applications or even simple scripts.

So tell me /prog/, what Lisp dialect should I learn or at least what are the pros and cons of each?

>>2
Well, I'm not sure about it dying any time soon, but when inevitably some guy cites Quiklisp as evidence of its revival... it's just a fucking package manager written by some random dude. It may be portable package manager, but that at least some libraries to manage are about the least of what's needed to be called a usable language nowadays.