GitX is a git GUI specifically for Mac OS X. It currently features a history viewer much like gitk and a commit GUI like git gui. But then in silky smooth OS X style! User-relevant information can be found on the GitX Homepage.
You can help in a couple of ways:
If you are going to change the interface, PLEASE use XCode 3.1. XCode 3.1 actually produces xibs that are mergeable, in contrast to previous XCode versions.