Naked Light

Naked Light claims to be a new image-editing application for Mac OS X promising non-destructive editing, node-based compositing, “infinite resolution”, live tools, and pro tools that work in photographer-friendly units like “stops”.
Rather than deal with all this jargon, just download the public beta when it becomes available tomorrow and give it a try… the interface certainly looks appealing. Note they say it requires Mac OS X Leopard (10.5), and probably a decent graphics card, to run.