I am new to linux and very new to linuxmce, so I will not be much help with the integration, but I am fairly familiar with drupal and I think it would be the obvious choice over joomla. Huge community, grreat support, thousands of free modules, etc, etc.
If someone can intergrate this with linuxmce there is already a drupal module that does most of what is requested here. Homebox newbielink:http://drupal.org/project/homebox [nonactive] would provide the ui for this. You can add google gadgets (calendar, mail traffic, directions, etc.) or your own data and drag, drop and resize the "boxes". There may be a problem with dragging a "homebox" with a google gadget embedded in it. I have seen 1 issue posted related to this, so it may or may not work. I will look into that. It may be an iframe or java issue. Does anyone know about google gadgets? Are they iframes?
I am wiring my house now to install an mce network and would love to see this added.
Off topic: does anyone know about a 10.04 release? or boxee (or similar) intergration?