This is a library which makes it possible to skin Qt made Widgets using SVG files and the ARGB support of Qt 4.5. You can change the Borders and add new System Buttons.
It looks promising, but could really use to be LGPL, or perhaps linkware. It also could use blurring, which would appear to be possible using this method. This is the only method to make Vista-like effects in XP that I know of. I wish something similar were the standard Qt way of doing it, for additional XP compatibility with translucent, blurred windows.