Admin theme for node (add, edit) and user (edit)
If you want to use your selected admin theme when creating a node or editing an user, you can do this easily with a very small custom module. In your custom module's hook_menu(), add this (outside of the $may_cache block):
<?php
if ((arg(0) == 'node' && arg(1) == 'add') || (arg(0) == 'node' && arg(2) == 'edit') || (arg(0) == 'user' && arg(2) == 'edit') ) {
global $custom_theme;
$custom_theme = variable_get('admin_theme', '0');
drupal_add_css(drupal_get_path('module', 'system') .'/admin.css', 'module');
}
?>Or whatever other set of path rules you want.
See also:

Has something like this been
Has something like this been contributed to drupal.org? I can't seem to find any modules that do this. I don't know the first thing about php or creating modules, but I'd really like to have this functionality on my site.
+1
Why not provide all the code needed for this 'custom module'?!?
UPDATE
======
I think I've found it here:
- http://drupal.org/node/242200#comment-793908
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