Just cranked out a new plugin today that might benefit domainers using WordPress to develop their names. This one does one thing so far: it places a customizable message at the very top of the page.
You can have it display anything you like. Typically, you might use “This Domain Is For Sale at MyPhatPortfolio.com”.
Download the Plugin here, extract and upload to your WordPress plugins folder. The configuration page is under the Settings menu. Enjoy!
You can see WP-Domainer in action at: