I stumbled across this site yesterday:  highscalability.com

"We started High Scalability to help you build successful scalable websites. This site tries to bring together all the lore, art, science, practice, and experience of building scalable websites into one place so you can learn how to build your system with confidence. Hopefully this site will move you further and faster along the learning curve of success."

This is really cool site/blog about building scalable architectures.  It contains lots of good info and overviews of some of the larger distributed systems on the net.  Definitely a regular stop for me.