Viva Vista
Viva Vista is a cross-platform Firefox Theme with new Vistas-like icons. It adapts Windows Vista interface on Firefox and works on Mac OS X, Windows, and Linux. The minimum Firefox version required is 3.0a1 - 3.0pre.
Tim Molter
2Believe
The Faithfully Firefox theme alters its interface with faith-related icons.
The Message Bible Verse Toolbar
This Firefox add-on shows random Bible verses on the toolbar.