Make sure you have 'include videos' ticked in the picture section of your iTunes sync. Also, I changed the folder from iPhoto to pictures folder as I was using Picasa and they wouldn't sync the videos. I then had to 'reload' all my pics and videos to iPhoto then change back the folder to iphoto in itunes then the videos were able to sync. They are stored in each folder that you have them in on iPhoto. Hope that makes sense.