I use a Swedish keyboard in Mac OS X and use the following setup for Emacs.app:
First I have KeyRemap4MacBook installed and I have it setup to change the left Option key to Command.
I then have the following in my .emacs:
(setq mac-option-modifier 'none)
(setq mac-command-modifier 'meta)
This makes Emacs treat command as Meta and ignore Option. Since the left Alt/Option key is remapped to command, this makes it work lite meta while the right Alt/Option key still works for entering special characters like @ [] and {}.
App specific Mac shortcuts like Cmd+C and Cmd+V no longer work, but global shortcuts like Cmd+space for Spotlight and Cmd+Tab for app switching do.
Update:
If you use iTerm2 as a Terminal, that has support for mapping only the left Alt/Option key to meta, which means you can still use the right AltGr/Option key for entering special characters. This also means you can use meta as normal inside Emacs running in the iTerm2 terminal.