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?

>>20
That's not saying much, care to explain why?