iChat
iChat is a free instant messaging application for Macs.
Firebug integrates with Firefox web browser to put a wealth of web development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page. This ia a must need for any designer building sites on there own. You will save so much time when using CSS coding.
LongTail Video is a free open source flash player that has lots of great tools to use. The player also allows for dozens of plugins and skins and as well offers the ability to monetize your site by adding AdSolution serves to pre-roll, overlay mid-roll and post-roll ads. Very useful.