Firefox 1.0 (preview) and Thunderbird 0.8
The Mozilla Foundation and its volunteers have been hard at work! They've just released Firefox 1.0 preview release, their fast, secure, and featureful browser which I've used since version 0.5 and Thunderbird 0.8 the email client. I would recommend both products to anyone who's ever been nailed with spyware, or viruses by using Internet Explorer or Outlook (or Express).
In particular, I cannot sing the praises of the browser enough. For browsing it offers quick navigation, tabs, integrated search box, and type-ahead find (just start typing and it searches in the web page). For web developers, the DOM Inspector is indispensable.