Photo Metadata Editing / Editor Are there any apps for OS X that can edit photos metadata (such as keywords, etc.) without all the bells and whistles of full stack photo management apps (such as Lightroom, iPhoto, etc.) with the option of embedding it in the file rather than keeping it in a separate place?

Some more info:


I want to retain my own folder structure with photos and don’t prefer programs organizing them in their own way and their own place.
I want to hard code all the metadata in the photos themselves so they are easily portable.
I want to be able to edit metadata in a batch when necessary
No command line tools, GUI apps only (thanks, @IconDaemon)
A few years ago, I pointed a photographer friend to ExifTool, a free, command-line based metadata editor. It looked pretty powerful and it did what she wanted. I haven't used it myself, so YMMV.