The Pixar shorts pre-order page has been up for almost a week, although it wasn't till a couple days ago they made any distinction (except price) between the DVD & Blu-Ray releases. The Cars Blu-Ray pre-order page was not there yesterday but appeared in my Amazon search results this morning. I assume Ratatouille can't be far behind...
Pixar Short Films Collection, Volume 1:
DVD: http://www.amazon.com/exec/obidos/ASIN/ ... eimprovemz
Blu-ray: http://www.amazon.com/exec/obidos/ASIN/ ... eimprovemz
Cars Blu-ray:
http://www.amazon.com/exec/obidos/ASIN/ ... eimprovemz