If you are looking for DVDs from past Microsoft conferences (MMS 2007, TechEd 2007, etc.), they are available online through the Microsoft Event DVD store. See http://shop.ecompanystore.com/mseventdvd for the details.
For those that wanted to attend this year's conferences but weren't able to, these DVDs should be available too within a few months after the completion of the conference. I hope pricing will be close to last year's.