<p>Working with Mircosoft Office Sharepoint Server 2007 (standard edition) what is the best way to place a site collection being developed under version control?  We're using Subversion for all our other (non-sharepoint) projects but I'm just not sure how to approach MOSS.</p>

<p>What needs to be placed under version control to ensure we have everything we need to rebuild the Sharepoint Environment?</p>

The question is sort of vague has you do not mention how you develop it. If you're just doing out of the box modifications on a site collection via the interface you have available in sharepoint it sounds like you need to do some kind of "backup". I don't think you can export a site collection as a template :P
If you're doing actual development, coding features that do site provisioning, web parts for that, custom page layouts and whatnot, I would suggestion copying the structure you have in the /12/ hive on your sharepoint in your visual studio. Place all the artifacts you have in the right folders in your solution and that makes it very easy to deploy, either just by copying and calling some stsadm commands or by making a new manifest.xml file and a .ddf file which you can then add to your solution repository on your sharepoint installation.