200 Points of Light
I still occasionally keep an eye out on the old HyperCard mailing list, and recently someone mentioned a stack called 200 Points of Light. The link is to a YouTube demo movie of this ancient HyperCard stack.
Essentially, it's a kind of spatial 3D interface (technically, it just uses fake perspective, so not even that) that uses the different dimensions to sort stuff by various criteria and allows filtering by others. It's a very simple approach (and can as you see be implemented with simple tools as well), but with faster computers, higher-resolution and colored graphics and all that, it's the foundation for any useful mix between 3D and Spotlight.
That reminds me, anyone else hardly use Spotlight? I use it mainly for the same stuff as I used to use Find File, and after that Finder's "Find" menu item and Sherlock. It's not made things that noticeably faster, though it showed some promise originally. I hope that changes with some of the Leopard back-end improvements...