libexif-iphone
I needed a way to work with EXIF data on the iPhone. There is already an Objective-C library called iphone-exif, but this is only available under the GPL license, which basically means you cannot use it in closed source projects.
libexif is a plain C library created by Lutz Mueller and others, released under the LGPL license.
I didn't manage to get it to build for the iPhone with the provided configure scripts and makefiles, so I created an Xcode project. As a side effect, it can now be more easily integrated with other Xcode projects: just add a dependency, add the folder to your header search path and link to the built product, and you're off.
Download (480kb tgz file)
You can read more about the changes done to the original code in the libexif-iphone.txt file that's included.