Powerbase (the Progressive Technology Project's hosted CiviCRM program) provides a Drupal site for your CiviCRM database, but, even though it's in Drupal, you can't use it for your web site. Your web site must be hosted elsewhere. This approach is becoming increasingly popular as organizations move from Drupal, Wordpress and Joomla to new web site platforms, or simply don't want their web site vulnerabilities to lead to a compromise of their database. Keeping your web site and database at arms length gives you both this flexibility and security.
However, there's a problem: How do you give users a nice seamless transition from your web site to a CiviCRM contribution form?
Up to now, you have to create a theme on the CiviCRM site that mimics the theme of your web site. Sadly, this is labor intensive, imperfect, and always at risk of becoming dated.
You can specify which web sites are allowed to post data this way, decide which profiles or contribution pages should be allowed to post data, and then you just have to add the code to the web site and you are off and running.
Please take it for a spin and open issues if you find problems.
Currently, it only works with the simplest of Contribution Pages and is only tested with the dummy payment processor and Stripe. The goal is to extend it to include event registration, petitions and more. Feedback and patches welcome.