I would like to include a common sidebar in one of my page templates. The sidebar would contain content that would be static across all pages that use it (i.e. not editable on a page by page basis)

I know I can simply add a PHP include file for the sidebar, but how can I make that sidebar editable in C5 so that the changes are available to every page that uses the sidebar?

I'm sure there is an easy way to accomplish this, although I can't find it anywhere.

Any help is greatly appreciated.