IronFox for OS X sandboxes Firefox for more secure browsing
One of the major draws of Chrome is that it runs in a sandbox, making it one of the most secure ways you can browse the Web today. The catch is that people have to use Chrome to gain that extra measure of security, and let's face facts here -- Chrome and Chromium only hold a fraction of the market share that Firefox has earned over the years.
Thankfully, Firefox users on OS X now have the option of using IronFox, which is simply a shell-script wrapper which starts Firefox in its very own sandbox. The only catches are that you must be running OS X 10.6 and Firefox 3.6 or newer. It's not a bad deal, considering all you're really doing is opening the Firefox you already use with a different icon.
IronFox creators say that while it only functions on Snow Leopard at the moment, that they do plan on a backport for Leopard sometime in the near future (when they find the time to work on it). Tiger users won't be able to take advantage of this since the kernel in 10.4 isn't built to handle it. (Sorry folks)