I'm closing down a Google Apps domain because the domain name is moving (donated) to a new owner. Since I don't know what happens to the data after I transfer the domain name I've so far:
- Exported the "Sites" pages using a Data Liberation Tool
- Deleted all the existing site user accounts
My next step is to get a local copy of all the documents. Again, the DLF has directions. This turns out to be built into the Docs framework. On export you can specify a file format, I chose RTF for documents, Excel for spreadsheets, and native for the rest (PDF).
I also made sure so share all the documents with my personal account, but I wasn't able to transfer ownership. Currently that's not supported in Google Apps.
We had the non-profit version of Google Apps (free from Google) so we had all the yummy pro features, like the ability to associated a secondary domain. I have some I could use and I considered doing that to provide a way to access data post transfer, but I decided to skip that step in the interests of time.