Using MediaWiki behind http authetication was always slightly annoying in the past. One would have to:

  1. Login with their htpasswd credentials
  2. Create account if it did not exist already
  3. Login with their wiki credentials
  4. Remember both sets of credentials

This extension reduces the previous four steps into one simple step.

  1. Login with htpasswd credentials

The extension can be downloaded at http://people.mozilla.com/~oremj/HttpAuthPlugin.php and setup instructions at MediaWiki.