Dear Paolo,
You may try SDF: [...] They provide free shell acces to OpenLisp, a good ISLISP system (type `lisp' at the prompt). ISLISP is not Common Lisp, but is "culturally close".
Thanks for pointing out. I'll look into it. Maybe there's even a textbook about it in the local library. Paper's easy to stare at than screen.
Matthias