How to create a non report based dashlet
If you're on Drupal, you can use the civicrm_views_dashlets module for a no-coding solution.  Not only can use create a view that shows a single page (which is editable like any other page), but you can use Views to show more complex content.  

For instance, when I worked on a CiviCRM-based SaaS a few years back, we created our own "news" dashlet by publishing an RSS feed from a central site, which was picked up by the Drupal Feeds module to populate the View.