I had this in mind for a loooong time. Using private pages was a hacky way of getting things done with the older WordPress. As Lorelle had suggested, I have put together a very simple plugin – bits – using custom post types feature of the newer WordPress versions.
bits is used to manage individual content pieces, and retrieve them anywhere in the theme. The plugin provides a shortcode that you can use in pages and posts, and a function to use in templates. Once you place the plugin in the plugins folder and activate it, you can use [shortcode title='Title of your bit'] or show_bit( 'Title of your bit' ); function where you want to display the bit. I will add details to the readme file.
We can call it a beta though. It was put together very quickly, without going through much testing. I would like to know if you find something wrong with it or if you want something more from it. Feel free to download and/or modify the plugin. All feedback is welcome, even if you have something like “This is the most useless plugin I have seen!” 
I will submit it to the WordPress plugins repository if someone other than me finds it useful and after enough testing.
