We recently started leveraging the Reusable Content list to supply user-editable content to one of our interactive online forms and outbound emails. This allows the content owner to tweak the content as required as this content isn't locked away in custom code or resource files—no build and deploy required and the content management system is even used as such (whatdya know?!).
The Reusable Content list is provisioned by SharePoint when the Publishing feature is enabled; it allows users to define content snippets that can be maintained in a single location and updated automatically wherever they're used. You can optionally treat a reusable content snippet as a template—an editable copy is inserted into the page instead of a read-only, auto-updating view.
Reusable Content list items are pretty straightforward and, most importantly, contain a single HTML (rich text) field. SharePoint naturally displays its rich text editor around this field in edit mode so the edit user experience is similar to editing page content.
Unfortunately HTML fields in SharePoint are smarter than they should be and (in MOSS 2007), the product will mangle some content. I recently discovered it refuses to play with background-image style—they're silently removed whether they're inline or in an embedded stylesheet. (And yes, I know, inline styles are evil but this snippet was actually being plugged into an email so everything had to be self-contained).
Despite the tricks SharePoint plays on you with "managed" URLs, it seems the rich text field also stores URLs pointing to content within the current site as relative URLs. Absolute URLs are converted automagically but you'll never really see this until you pull the content out via the API.
To address this, we replace all relative URLs using the regex below (note the URL group) (is using regex to parse HTML bad? You be the judge). You may want to use SPUtility.GetFullUrl() to convert individual URLs.