Official Sony Sites
Official Playstation Site - Sony's official US website.
Open Platform Site - Sony's site for detailing how to boot other OSes on the PS3.
PS3 as a game machine sites:
Playstation Univeristy- Looks to be a pretty fancy site focusing on gaming use of the PSE (I should call it the "expected" use of the hardware).
PS3Land - Playstation 3 focused news site.
PS3Focus - Another "news" site that focuses (sorry for the pun) on the Playstation 3.
PS3 For Linux: