UPDATE: New plugin here for WP2.9
Long time ago a guy that worked for me wrote this flippin awesome plugin for WP 2.3. Needs to be updated to use wordpress 2.5+ Care to help?
It allows you to define multiple editable regions per page template.. then simply select which region (top of WYSIWYG) to edit. We used icons in the PageTemplate box on the right to make it easier for users of our DIY web service, flare9.com. In the template file you just echo that region out by a function multieditDisplay(‘yourregionname’);
Been sitting on it for a while, it needs to be updated to work with WP 2.5+. Care to help? Plz download it and go to town, ping me with any questions. There is a real short readme… included.