Web development on PowerPC
I still use Mac OS X 10.5.8 for web development. It has a built-in Apache server with PHP, but I easily installed MAMP.

As for node.js, the V8 engine under the hood requires Intel CPU, but RingoJS and Rhino work fine. There is Rhinode for node.js-like API on top of Rhino, but I haven't tested it.