Mozilla Firefox for U3
Mozilla Firefox is a fast, full-featured Web browser. Firefox includes pop-up blocking, tab-browsing, integrated Google search, simplified privacy controls, a streamlined browser window that shows you more of the page than any other browser and a number of additional features that work with you to help you get the most out of your time online.
Please Note: With the latest release of Firefox (4.0), I have been looking into whether Firefox is still portable. If I succeed in making it portable, I will update it here.