The Information Retrieval Methods PDF by Christopher D. Manning, Prabhakar Raghavan and Hinrich Schütze is not only gratis, but a good resource on all kinds of Information Retrieval topics: the boolean model, the vector space model, tf-idf weighting, language models etc.
The Linux Administration Handbook (second edition) is $42.89 on Amazon. From the
/proc pseudo filesystem to information on user accounts and GRUB, this book is one of the most comprehensive Linux sysadmin resources I own.
According to Google. The final figure isn’t as interesting as the post detailing how they came up with it – a process that started by answering a seemingly simple question: “What counts as a book?”
An upcoming book by Mark Pilgrim of Dive into HTML5 fame. Available for preorder now, releasing March 15.
Fascinating general science book written in layman’s terms.
A lesser-known but informative online book by Google.