First off we have a simple interface tweak that goes a long way to unifying the look of your system. Adam's new QuickTime Plugin Controller replaces the old icky Aqua bubble quicktime plugin interface with a sleek platinum/unified/post-brushed metal look.
Next are two replacement icons; one for a certain flammable fox, the other for a Preview alternative. The Firefox icon touchup fixes dock weight issues (how close it is to the other icons) as well as making the whole package a bit smoother.
The Xee replacement set actually contains replacements for both the actual application icon as well as the status bar. Xee is a replacement for Preview and available for free download.
Finally, we have the 9.3% complete interface-lift for Google Earth. This package will replace the application icon as well as modify certain UI elements such as toolbar icons and the sidebar to make them more Mac-like.