There is a special Facebook page to watch the Star Tours opening ceremony webcast from Disney's Hollywood Studios. The ceremony is today, Friday 5/20 at 10:15am Eastern.
Star Tours - Watch Live Webcast | Facebook
Also: Disney Parks Blog will start their webcast coverage at 10:00am Eastern on their website.
Star Tours Grand Opening Webcast from Disney
They will also stream it on the Disney Parks YouTube page.
YouTube - ‪DisneyParks's Channel‬‏
Edit: Ceremony recap: http://www.wdwevent.com/startours/