Common Lisp for Schemers

What's the best way for a Schemer to learn Common Lisp? It seems like Scheme itself is a more beautiful language, but the efforts made by many implementations to make Scheme useful "in the real world" lead to a big ball of mud™. Does Common Lisp avoid this problem? Should I keep trying to learn different Scheme implementations instead until I find something I like?

>>21
If you go down that route, a mess of pointers and malloc's with side effects everywhere should pose no difficulty to a Real Programmer. It's subtler than that, and that's a subtlety that a Common Lisp programmer should grasp, using a language which compromised the concerns of every implementor of Lisp languages at the time.

On a side note: Google no longer presents me captchas with house numbers, why is that? Is my IP/cookie "trusted" now? Is it because I fed it with randomly generated numbers?