Once, (in the 1960s) there was one language called LISP.
Nobody uses that now, and LISP developed into a family of languages.
The most prominent ones currently are Common Lisp and Scheme, and there are some more newer ones like Clojure, LFE, and Hy.
If you’re planning to do AI in Lisp, you’re looking into Common Lisp.
Common Lisp was standardized by an ANSI committee (think about C) so there is no central force that controls the language. Hence there is no such canonical webpage (as there is no canonical C homepage).
If you’re looking into resources to learn lisp, it’s better to look at the sites below:
‘Practical Common Lisp’ is *the* book to learn Common Lisp.
Some chapters about tooling is outdated, look at the ‘Common Lisp Cookbook’:
If you’re looking for an editor, I would suggest looking Emacs, but if you’re lazy and you’re not going to learn esoteric keybindings, try Atom & SLIMA. There are also plugins for vim / SublimeText, but I have no previous experience with them.
For libraries, the ‘Awesome CL’ list is great:
Hope this helps.