readers, i give you beryl.that's an XFCE4 terminal being minimized. my cube is transparent, so you can see a corner between two desktops in the background.
for the record, i'm running the january 5th build of XGL, the SVN beryl ebuilds from the xeffects overlay, and XFCE 4.4. my graphics card is an ATI mobility radeon X300, running with ATI's fglrx driver. took me roughly a day to get it all together, but it's running beautifully.
i'm going to back to burning up my windows now.