BTW, I'm one of the few proud owners of a copy of "On Lisp", one of the best computer science books ever. The fascinating thing is that Paul Graham wrote Yahoo Shopper in Common Lisp and made millions doing it. In LISP!
I've been thinking about Lisp a lot recently.
I think Lisp could use a few small extensions. One would be to make CONS sub-classable. This would help, for example, with XML, kinda like Perl 6's [vapourware] per-scalar, per-symbol property values, but I also see much value in writing a compiler: code analysis information could be stored in new fields in the conses of an s-expression without modifying the form of the expression. Such an extension would also require an extension to dot notation so extended conses could be printed and read.
Another extension that would be nice is what I think of as "forward closures", much like Pascal or GCC local functions, which are closures that are defined only as long as the parent function instance does not exit. There is a safety issue with such forward values, of course, but the value of forward closures is that it can make continuation passing style code more efficient by not requiring heap storage for captured variables. And this (CPS) is needed to implement logic programming languages like Prolog or Icon. And I would really like to be able to program in Lisp with Icon semantics.
But this is all kinda academic... I'm not working on that sort of stuff...