Xenu
Helpful software that checks for broken links on a website.

XML
XML stands for Extensible Markup Language (filename.xml) - a scripting language that allows the programmer to define the properties of the document.

Yahoo!
Pioneer Web directory and one of the 3 main search engines -- (Google, MSN and Yahoo).

Zeitgeist
The Google Zeitgeist page reflects tidbits of information related to the search behavior of Google users, pulling together interesting search trends and patterns.

Zip
Refers to a file compression format.