Here is the schedule for the big-scale pre-E3 and during-E3 events.
June 6th Update - Check out the official E3 insider - live crowd activity tracker and many other things. http://www.e3insider.com/
Live Microsoft E3 stream, about to start - http://e3.gamespot.com/press-conference/microsoft-e3/
Live Gametrailers TV stream - http://www.gametrailers.com/netstorage/e3/e3-live.html
SpikeTV - online stream for outside USA/Canada - http://www.watchfomny.com/Video/USA/01/spike/spike.htm
Official E3 Insider Twitter - http://twitter.com/e3insider
Microsoft 10AM-11AM PT, 1PM ET
EA 11:30 AM - 1:30 PM PT, 2:30 PM - 4:30 PM ET
Ubisoft 1:00 PM - 3:30 PM PT, 4:00 PM - 6:30PM ET
Sony 5:00 PM - 10:00 PM PT, 8:00 PM to 1:00 AM ET
Nintendo 7:15AM PT - 10:15AM PT, 10:15AM ET - 1:15PM ET
Show floor opens @ 12:00PM PT, 3:00PM ET
Nintendo roundtable, number one @ 5:30PM PT - 7:30PM PT, 8:30PM ET - 10:30PM ET
Nintendo roundtable, number two @ 5:30PM PT - 7:30PM PT, 8:30PM ET - 10:30PM ET
Sonic Party 6:00PM PT - 10:00PM PT, 9:00PM ET - 1:00AM ET
Round up of the events.