Password protection

Hi, just wondering... Is it possible to password-protect any single application / file / folder?

I know that the home folder can be password-protected by firevault, but what about other folders or just a particular application?

You can change the permissions on any file by going into its details (highlight the file and press Command-I). I know this isn't password protection, but it will keep other users on your computer from being able to access the file.