Ooh, tough one. You could use F10 in Exposé (runs in Tiger and Leopard Finder by default). Once you hit F10, all the windows for the current application fan out. Then you can use either the mouse, or the arrow keys (followed by return to select) to pick which window you wish to bring to the foreground.
There’s also a $15 app… LiteSwitch X, which significantly enhances command-tab.
Hope that helps you think a little more highly of Finder!

Cheers,
Lyle