Nu is object-oriented and functional. It is written in Lisp-like s-expressions but conforms to no preexisting Lisp standard. Instead, Nu was designed to follow Yukihiro Matsumoto’s “Principle of Least Surprise” while staying tightly integrated with C via the Objective-C runtime and object model.
Objective-C is an object-oriented extension of C that provides powerful messaging primitives, deep runtime introspection, and dynamic binding, all important tools for bridging to dynamic languages. From that, Objective-C has been bridged to many dynamic languages: Python, Ruby, Perl, Scheme, and many others. It has also been used to build at least one completely new scripting language, Philippe Mougin’s F-Script.
Nu excites me, both as a language geek, and as a software developer -- a dynamic language that's designed to work with Objective-C from the ground up is going to make it a lot easier to develop interesting applications for Mac OS X. I'm really looking forward to working with Nu in the future.