Webopedia is a great site to look up phrases, terms, and abbreviations connected to computers and the internet. It's strong point is that anyone from beginners to advanced will find it useful. The site description is spot on: "....Webopedia provides easy-to-understand definitions in plain language, avoiding the use of heavy jargon when possible so that the site is accessible to users with a wide range of computer knowledge."
The Term of the Day, Quick Reference and Did You Know sections are full of useful articles.
I also like the WeboBlog and found the Categories page helpful for quick navigation.
Some sections like the Term of the Day are sponsored but there's a refreshing lack of ads where the content is.
There are ads on the site but I found them to well placed and non-intrusive. If you decide to get the free eBook you'll need to create an account while the newsletter needs an email address.