Note: core stuff like algorithms, new patterns etc.
not fads like RoR, Ajax...
Stuff that usually sits in abtruse papers, out of mind for the average developer.
Accessible to the average developer, and in a form more easily digestible
(studying research papers is not practical for all).
When I picked up the Cormen book recently, I saw lots of new stuff I didnt learn in College.
Having strong networking knowledge is very useful and can be applied to cool areas of growth such as the Internet and mobile devices. I took a graduate level course in networking as an undergrad and it was one of the best decisions I've made.
If you want to teach yourself, I recommend the following books:
Computer Networks by Andrew Tanenbaum - This book is from 2002, but is still considered the Bible of Networking. It covers all of the advanced topics and is great as a reference. You can pick it up used for cheap.
TCP/IP Socket in ____ by Michael J Donahoo - This is a series of books that cover network programming in different languages. There is a C/C++, Java, and C# version of the book that I know of, but there might be more now too. These books are very concise and to the point and teach you everything you need to know to write advanced network programs.