Mike Simonds released 2 scripts over the past few days that will create copies of your Salesforce schema into MySQL or Oracle databases. I haven’t tested either of them, but I think this could be pretty handy. Of course, you’ll need to have additional scripts actually bring your data over from Salesforce to these databases, but this is a start. Learn more about the scripts using the links below.
If you try these, feel free to comment here about how it went. If you actually want to let Mike know about your use of the scripts, you could submit replies on his site or at his forum postings about the functionality (Oracle, MySQL)