I'm not sure how long this has been available, but check out this revealing map of E3's south and west halls:

http://e3expo.com/exhibitors/images/west_south_halls.jpg

(You may need to scroll right to see Nintendo's area.)

Although the Big 'N' does have probably the largest chunk of floor, they may be using some of it for an employee lounge-type section like they did last year. Note that Sega is in the same location as last year, but with half as much floorspace, while Microsoft, surprisingly, is not even in the main hall! MS also has a noticeably small booth compared to Sony and Nintendo...hmmm. Also interesting is the location of Enix on the main hall, since their presence at least year's show was almost nil. Thanks to Mikey for bringing this map to my attention.