Populating sidebar with the contents of a certain page

I have a client who’d like to put a long list of testimonials on his sidebar.

Seems like the simplest approach would be to let him edit a page, and show the contents of that particular page on the sidebar.

This will be a site-wide change, so I think I’d like to have sidebar.php say something like “echo page_contents(2)” or whatever.

I’ve tried a dozen different searches in the forums and can’t figure out where the trick to doing this might be located.

Any suggestions?

[I posted this same question in the Plugins & Hacks section this morning, but it’s still not showing up and it’s listed on my profile as a “reply” rather than a new thread. I don’t understand what’s wrong, there, so I’m re-posting it in this How-to and Troubleshooting section. I apologize for any breach of protocol.]