Instead of packing images, a good alternative is to use relative paths. When you pick the texture put // in front of the file name relative to the local folder. For example, say you have a folder called images in the same folder as your .blend file. After picking the image from the Texture buttons you can delete the path before the word images and replace it with //images. So for example, if it was: /Users/nick/blendExample/images/dog.psd, make it //images/dog.psd.
This makes it far easier to share .blend files with textures