Fast User Switching, that allows a user to remain logged in while another user logs in feature, featuring the desktop on an animated cube (the effect is only seen on systems with Quartz Extreme). Windows XP has a similar feature without an animated cube.
Exposé, a program to help the user manage windows, especially large numbers of them.
Apple KnowledgeBase Page (http://docs.info.apple.com/article.html?artnum=300569)
References
Apple Computer, Inc. (2003). Mac OS X 10.3.2 Update: Information and Download. Retrieved December 19, 2003, from http://docs.info.apple.com/article.html?artnum=120288
External links
Apple: Mac OS X Panther (http://www.apple.com/macosx/panther/)
Apple: Mac OS X 10.3: Chart of available Mac OS software updates (http://docs.info.apple.com/article.html?artnum=25633)
Ars Technica: Mac OS X 10.3 Panther (http://www.arstechnica.com/reviews/003/panther/macosx-10.3-1.html)