I began your blog and following a couple posts made the decision I did not such as the /2009/03/26/foo-bar plan for Web addresses (I transformed to simply /foo-bar). As well as the couple posts published before I transformed this, I wish to add rewrite rules therefore the old Web addresses don't break.

I have attempted every variation from the following I possibly could think about within the .htaccess file, with no success: (observe that everything here except the "first-publish" and "second-publish" lines is wordpress boilerplate)

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /

RewriteRule /2009/03/25/first-post /first-post
RewriteRule /2009/03/26/second-post /second-post

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

Any ideas?

Try the Permalink migration plugin from Dean Lee.

Try

RewriteRule ^\d*/\d*/\d*/(.*) /$1

A hacky solution which i just attempted that actually works would be to really produce the sites and subdirectories 2009/03/25/ etc after which add a catalog.perl file that contains the next:

<?php
header('Location: http://example.com/first-post');
?>