NetLingo – the award-winning dictionary of Internet terms. It contains thousands of words and definitions that describe the online world of business, technology, and communication. They’re there to educate and entertain you about the lingo used in the online world. They have articles, a “cheat sheet” and much much more:

An online dictionary of Internet terms
You can download the ebook version
You can download Netlingo as a PDF

And they have other internet resources as well including:

Acronyms
Text Messaging (IM)
Smileys & Emoticons
Web Coloring Tool
File Extensions
Useful Business Links

And different categories which include:

Acronyms & Shorthand
Online Business Terms
Online Jargon
Online Marketing
Net Organizations
Net Technology
Net Software
Net Hardware
Net Programming
Technical Terms

You can brush up on your Internet lingo here:
http://www.netlingo.com