Thanks, `{vb:raw relpath}` is the best answer. I found this when I searched for "current URL in vBulletin templates".
The variable spits out the current page like `$_SERVER['PHP_SELF']`, without anything else. If you are on the Forum homepage, for example, it won't spit out anything. Here is how I used this code to submit an email signup form back to the current page on our site:
Code:
<form action="/forum/{vb:raw relpath}#footer" ...