According to this BethBlog post, the E3 Fallout 3 trailer is to partially air on Spike TV at 1.00am (presumably PST) on Saturday morning. From the site:
E3 kicks off next week, but if you want a first look at the new trailer for Fallout 3, be sure to throw back a few energy drinks so you can stay up until 1AM on Saturday morning to watch GameTrailers TV with Geoff Keighley: E3 Preview on Spike TV. During the broadcast, they’ll be showing a glimpse of a never-before-seen Fallout 3 trailer that’ll be shown during E3 next week.
It’ll be on the internet immediately, so watch for it on Sunday morning, European types. Thanks, Gaming Today.