Free Folder Encryptian Software?

Disk Utility (in your Utilities folder) should do the job. You can use that to create encrypted disk images. If you make a sparse disk image it will grow in size as you add files, like a folder.



EDIT: I just tried this out and it doesn't grow like I expected. To make it grow you need to go into the command line. Have a look here and here.

To clarify it does the job but you have to set a finite size. So i guess you might as well make it a read/right image, I'm not sure what the difference is.

 

gpg. See here for details www.gnupg.org/ This is pretty much the standard if you need to encrypt or sign a file.

Mac OS X can encrypt a disk or a user's home directory but you asked for "files".

Edit: Google found this:
http://macgpg.sourceforge.net/