How could you use Ubuntu to create your own distro of XBMC (ex. Boxee Plex)? Is there a site (I checked XBMC's wiki and found nothing) that tells you how to do this?
2 Answers
You may find the answer in the development of XBMCbuntu, which is now the recommended live demo-and-install media for XBMC, as of XBMC 11, “Eden”.
If you are expecting a straightforward how-to procedure, I think you will be disappointed. XBMCbuntu is the result of a lot of complex work by a lot of people, and the best way to understand how it is put together is to examine the source code repository.
sudo add-apt-repository ppa:team-xbmc && sudo apt-get update && sudo apt-get install xbmc
For a thorough installation guide for lots of media stuff check this question on AskUbuntu. The accepted answer covers a lot of the multimedia application installation and skinning.
If the question isn't how do I install xmbc, but how do I make a respin you should check out turnkeylinux tools or remastersys.