Mozilla recently introduced the first alpha release for the upcoming build of their popular browser, Firefox 3.6. Codenamed "Namoroka" Firefox 3.6 Alpha 1 is intended for developers only, and offers quite a long list of bug fixes as well as some performance tweaks.
Given its unfinished nature, Mozilla recommends that that only developers and testers install Firefox 3.6 Alpha 1. That said, if you are the daring type versions for Windows, Mac OS X, and Linux are readily available. Be sure to tell us what you think in the comments!