<p>I want to get my databases under version control.</p>
<p>I'll always want to have at least <em>some</em> data in there (as <a href="https://stackoverflow.com/users/80/alumb">alumb</a> mentions: user types and administrators). I'll also often want a large collection of generated test data for performance measurements.</p>
<p>How would I apply version control to my database?</p>

This is one of the "hard problems" surrounding development. As far as I know there are no perfect solutions.
If you only need to store the database structure and not the data you can export the database as SQL queries. (in Enterprise Manager: Right click on database -> Generate SQL script. I recommend setting the "create one file per object" on the options tab) You can then commit these text files to svn and make use of svn's diff and logging functions.
I have this tied together with a Batch script that takes a couple parameters and sets up the database. I also added some additional queries that enter default data like user types and the admin user. (If you want more info on this, post something and I can put the script somewhere accessible)
If you need to keep all of the data as well, I recommend keeping a back up of the database and using Redgate (
http://www.red-gate.com/
) products to do the comparisons. They don't come cheap, but they are worth every penny.