A new Smalltalk for OS X. Integrated into Aqua. With all the tools you could wish for. Unfortunately only from OS X 10.3 onwards - too bad, I would have liked to take a look at it, but I'm still on 10.2.8 ...
Anyone who can give it a try - the beta is freely available. I'd be curious to know what it's like. Smalltalk used to be one of my favorite languages - though that was before my contact with Lisp machines and back in DOS times