Webopedia
Webopedia is an online dictionary and search engine for computer, Internet, and technology terms. Information and useful links relating to those terms are provided. The site also includes Internet news, Web development topics, and a wide variety of Net resources. Users may search by keyword or category.
For additional information on Webopedia, you can see this review on Rick's Daily Tips: http://www.ricksdailytips.com/webopedia/