Q. How do I upgrade from SharePoint 2003 to SharePoint 2010?

A. As it turns out, by way of MOSS 2007. Which seems kind of silly, but actually works out great, since you can use an evaluation version of MOSS to do it:

Planning for Upgrade from SharePoint Portal Server 2003 to SharePoint Server 2010 - Microsoft SharePoint Team Blog - Site Home - MSDN Blogs