Important: TenFourFox is not an official Mozilla product and is not an officially sanctioned build of Firefox. Further since this for the Mac I have not able to use this application, nor would I be able to provide any type of support. The reason for this post is to let Mac users who are on OS X 10.4 (or newer) running Power PCs that there is a way to get the new features that come with Firefox 4 and there is an alternative to Safari.
TenFourFox is a custom open-source browser built-off of the new Gecko 2 rendering engine and contains most if not all of the features that come with Firefox 4. This browser has been adapted to run on OS X 10.4 as well as Mac users who do not have an Intel Chip. This group of Mac users have been excluded from the official Mozilla Firefox 4 release.
For more information and to download see the TenFourFox site.