To the few lispers here, which one is your fave dialect and why?

Not really a Lisper, but given the "programmability" of Lisp syntax, you could argue that the main difference is namespaces, that is between a "Lisp-1" (e.g. Scheme) and a "Lisp-2" such as Common Lisp.

I'd certainly be interested in comments on Clojure (with its emphasis on immutability) and Shen for its optional type system and seeming all-round awesomeness.

@Wildgoose Racket is a scheme with an optional type system too, and an interesting one at that. I've heard a rumour that it's moving into dependent typing soon