I had this idea about a month ago to put video on buttons using CSS sprite sheets. The code and documentation for it is now release-worthy i think, so i'm posting the URL here; http://mediabeez.ws/ I welcome comments, feature-requests, bug-reports, bug-fixes, etc. Note: if you use 900 frames for 4 button states, the graphics can weigh in at 2Mb or more. But if you use only 100 frames total per button, it's in the <500kb range. If you're looking for a cheap reliable hoster without bandwidth consumption limitations, then by all means click on that godaddy ad link on my page ;-)
Oh, and the code is donation-ware, you may use it for free in commercial projects and all other project types.