CiviCRM Community Forums (archive)

Alternatively, you can use some handy Drupal modules to force certain pages to a specific theme.

install themekey: http://drupal.org/project/themekey

then in that configuration, you can configure a specific path to be in a specific theme. Meaning you can put in your contribute pages (and I believe it also accepts wildcards) and force them to a specific theme (all of this without hacking anything).

The one thing I am not sure about is if themekey will deal with the civicrm parameters in the URLs (everything after the ? in the url). So you might also need to use the path redirect module: http://drupal.org/project/path_redirect

once you have this, you can redirect your contribution page(s) to a drupal alias (like mysite.com/contribute) instead of the not-so-nice looking civicrm urls.