Yup Digi, its a 'Shuttle' (SN41g2)
See
Shuttle Website for more info.
Its a small form factor PC with an nVidia Nforce2 motherboard in it. Very nifty little beastie. Had to mod the fans a little bit to get the noise down though. The stock fans it comes with sound like jet engines.
...Unless of course you meant the Apple G4 Cube, which is an Apple G4 Cube *L*