I have most of my folders set to open with the defaults I’ve set for icon size, view columns, etc.; plus a few folders which have their own customized settings. In Tiger and earlier, there was a button on the View Options panel to restore a customized folder to the default view, but we lost this with Leopard.
To restore a folder to the default view settings in Leopard, open the View Options panel (Command-J, or View » Show View Options) then hold down the Option key. With the Option key down, the ‘Use as Defaults’ button will change to ‘Restore to Defaults.’