Watercolor Arrow - This theme looks so cool with a light colored taskbar, blue menu and funny hand-drawn type icons.
Wood Visual Styles - Transforms everything to wood! This theme is tested in Windows XP SP2
Kupo XP 2.0 - A very minimalistic design available in 5 colors.
Aurum VS 1.1 - A bit of Vista's Aurora look.
DUO - A mixture of Vista and Mac.
Simplebox - This time it's Fedora.
animus - A Mac like blue and white theme that works great with Mac icon set.
OSX Tiger V - Give Windows the Mac look. Very nicely done.
VistaPerfection X4 - One of the best looking Vista theme for Windows XP.
Dream LH 1.0 - Another theme with the Vista look, but darkish and black explorer window and task panel.