I just finished reading the book Building Scalable Web Sites by Cal Henderson of Flickr fame. It was a very interesting read and covered quite a few things I wasn't expecting. Most of the code was PHP, which I've never worked with, so that in itself was cool to see for the first time. He covered a ton of topics, including walking through how they scaled Flickr. I got the most out of chapter 9: Scaling Web Applications. He also gives a decent overview of Web Services in the last chapter, which I wasn't expecting. The book was easy to read and some of the difficult topics he explained clearly and concisely.
Overall it was an excellent book and I would recommend it to anyone building web sites regardless of whether or not they're using PHP.
