How about considering a new data (post) type called 'Bits'. We would have Posts, Pages and Bits. Bits would be small tidbits of information, generally showing up within info boxes in the sidebars or as breakout information boxes within content areas.
We could then include the Bits by calling a simple tag such as wp_bit(100), where 100 is the ID of the Bit. We could apply styling the the Bits. Bits would be reusable in different areas across different pages.
I know that we can create pages and include the content within different areas of WP, but using Bits would be much cleaner. Bits are not Pages.
I wish I could write a plugin for this. Maybe someone with more skills than me??
Just my blue sky thoughts.