In Mac OS X, how do i navigate into a package from file chooser?

Open and Save panels have an option to treat bundles/packages as directories, but the majority of apps would never enable or use that option. (What I mean is, the developer, before presenting the open or save panel, can set an option, but most apps would never do so).

If you have a Finder window that’s open in the background, you can use the standard “drag the window's proxy icon to the open/save panel to change the current directory” method like shown in the images below:

Just drag any folder from the Finder window, or the proxy icon itself (you should be able to do it all from the app with the open or save panel, without it switching you to the Finder) and drop it anywhere in the open panel’s file area.

Hit ⌘+shift+G to get a prompt to "Go to folder".

From here you can type (with tab completion) "~/Pictures/Photo Booth Library"