www.webkit.org -- this is the dev version of Safari. The new prerelease (very stable) is so FAST that I've dumped Firefox for good. Even tho I have to do without the nice greasemonkey scripts for YC News.
The first question I had: is there some kind of Adblock clone? Answer: multiple. See pimpmysafari.com for all the pluginz.
I'm sold on this new browser. Makes my old PB G4 run like it's on an intel core duo.
Oh, and you can run it on Windows too, and Linux. Didn't mention this because I think the essential plugins only run on the Mac.