Head on a Stick started life as a mobile phone game developed by Game Snacks (http://www.freegamesnack s.com). Now it is available as a free Flash game from the original authors, so even more people get to play it!
The game features 5 different heads, ranging in size and weight and 5 different locations from this world and beyond. Finish all 5 levels and it's back to the start, but with heavier heads to increase the difficulty.
The game also contains code to allow you to add it to your mySpace profile, if you have one. See http://www.myspace.com/he adonastickgame for an example!