[soegaard]

First of all both Common Lisp and Scheme are excellent languages with impressive implementations to choose between. Furthermore if you learn one of them, you'll be able to learn the other one in no time.

Instead of comparing languages, I'd suggest you pick between implementations. This suggestion might seem odd, but the Scheme standard (R*RS) is very minimal, which imply that all major Scheme implementations contain many, many libraries and language construct not mentioned in the standard.

I my self is a Racket user, which of course makes my view biased. Here are some of the reasons Racket is the perfect choice for me:

   - programs runs on Windows, OS X and Linux 
     with no source changes

   - the installation is pain free

   - the documentation of the language and libraries 
     are in a league of its own 
     (http://docs.racket-lang.org/)
     [that said, the Common Lisp spec is also very good]

   - the language is clean with a very good module system
     that supports macros the right way (IMO)

   - the community is very helpful (ask if there is a
     library/construct/feature you can't find 
     --- odds are you the wrong place)

[zeynel1]

"After all, a picture is worth five hundred “hello world”s."

Thanks for the link to Racket tutorial.