There is so much technical information available, it is difficult to know where to start. With so much data on the Internet, it can be hard to wade through all the bad sites to find the gems of useful, in-depth information. And, in the bookstore, with each book costing about $50, it can be intimidating. I've provided this reading list to solve exactly that problem.

What should I read?

Many hackers think that all the information they could ever get from a book is available on the Internet for free, so why purchase one? While this line of thinking is correct, books are a much more efficient way of learning, and I find it is often worth the money.

Where should I buy them?

Although I've provided links to amazon.com, I've done so only so you can get a good description of the book. I strongly recommend you support you local bookseller.

Security Focus.com Elias Levy's BugTraq mailing list is _THE_ source for new security vulnerabilities. While they preach full disclosure, this is not truly the case, which is a thorn in the side of hackers.
The HoneyNet Project An interesting project to catch hackers "in the wild".
Hacker Resources Writeup on many techniques, focuses on NFS and covering your tracks. Some of it is outdated, however.

Periodicals:

Phrack Magazine    --    Always cutting edge technical information. Issues 30 and above are required reading for any hacker.
2600 Magazine   --   The Hacker Quarterly, is named for the frequency, 2600Hz, which could hijack long distance phone lines. 2600 is one of the longest running print magazines around. Its editor, Emmanuel Goldstein, leans far to the left, and often steers the 'zine towards political ranting. However, there are plenty of technical gems to be found.

Books (Technical):

Internet Security - Professional Reference New Riders Publishing, ISBN 1-56205-557-7. I purchased this book in 1996 and I still use it all the time. Topics covered include: TCP/IP, Firewalling, Spoofing and Sniffing, and more. This book serves as a great introduction to many hacking techniques, and how to defend yourself. *This book seems to bnow be out of print*
Linux Socket Programming by Sean Walton, Sams Publishing ISBN 0-672-31935-7. This book is a must for any hacker wishing to transmit data across the Internet. Topics include Streams, Datagrams, Clients, Servers, Secure Socket Layer, and more. I've used it for numerous programming projects, including CUnap.
Inside TCP/IP - Third Edition New Riders Publishing, ISBN 1-56205-714-6. The definitive guide to TCP/IP, the protocol suite that drives the Internet. Every layer of network communication is explained in depth, from physical twisted pair, or fiber, all the way up to specifics of application layer protocols such as telnet and ftp.
Applied Cryptography by Bruce Schneier, John Wiley and Sons Publishing. Bruce Schneier is a well known computer security expert, and in this highly technical book, he dives deep into the little known and even less understood world of cipher systems.

Books (Fun):

Cyberpunk three or four true life hacker stories, Pengo, Mitinick, Morris, and more!
Takedown This is the true story of the life and times of Kevin David Mitinik told by New York Times reporter, John Markoff. It is fairly accurate, and quite an amazing story.
The Hacker Crackdown Bruce Sterling tells the story of "Operation Sundevil" the Secret Service and FBI's early years crackdown on many domestic hacking groups.
The Coocoo's Egg by Cliff Stoll, a computer expert who, while working at Berkeley's Computer Center, traced the activities of a young hacker. The East German hacker was successfully finding data on computers run by the United States government, and was selling it to the KGB. It is interesting to note that since the writing of this book, Cliff Stoll has become quite a "anti-technologist".

Movies (Fun):

Hackers If you haven't seen this, get a life!
Wargames The original Hacker flick.
Sneakers Many hackers prefer the realistic side of this movie to Hackers.
Tron Another must-see classic.
Takedown (French Site) If you haven't seen this movie, I don't blame you, because it has not been released in the United States, or Canada. This is a movie about Kevin Mitinik, produced by a major US studio. I have a copy that is available upon request for downloading, or if you're lucky, I'll ship you a CD.