Cal Henderson's guide to scalable web applications is a book that won't dissapoint you at all.
In the initial chapters, he covers from the very basics ( layered design, good source code control ) to more "complicated" aspects of Unicode, internationalization and localization. He goes on to give a deep-geek analysis of email support in web apps, complete with security problems. Remote services are analysed and thought over as well, and different formats like REST, XML-RPC and SOAP are not forgotten, of course, and they are also duly reviewed twice, pros and cons and all.
Probably chapters 8 and 9 are the most interesting of the book (not to undervalue the rest of the content), as they delve deep into issues and problems that many of us, being way too used to working on the software side of things, tend to disregard when designing application. And that is all hardware issues that pertain to scalable apps. Clusters, Replication, CPU bound bottlenecks, disk reliability, data centers, disaster recovery, spare capacity...all of this is perfectly and clearly explained and very well covered. Very illuminating for anyone working in any non-trivial web development effort, from the developers to the project lead.
Then he tops the book by reviewing, not so deeply, issues with monitoring and statistics (usage, trends) and public API exposure.
The book is geared towards the PHP / MySQL developer working on Linux, therefore all the many tools mentioned are for this kind of environment. However, in spite of working in a Microsoft environment, I found the book very illuminating all the same.
I learned a real lot from it, and I mean to review some chapters every now and then. Is there anything better you can say about a book?