@Scott B,
I just read a post on Justin Tadlocks Blog regarding this same issue.
The Solution
Use the default_content
filter hook and it to the themes function.php file.
Example:
<?php
add_filter( 'default_content', 'my_editor_content' );
function my_editor_content( $content ) {
$content = "This is some custom content I'm adding to the post editor because I hate re-typing it.";
return $content;
}
?>
You could add XHTML or anything you wanted to the $content string
When you click “Add New Post” you get: