Removing stuck or seized seatpost?

I went to adjust my seatpost today and it is completely and utterly stuck, I even hit it with a hefty hammer that I borrowed from some guys that were doing some building work and it did not budge after a few meaty whacks. The position is actually ok, I was only going to move it up 5mm anyway so it's not that big a problem. The only way I could think of ever actually getting it out should I need to would be to drill through it and stick a metal pole through and twist, this is obviously a bit drastic if there may be another less destructive way of getting it to move, any suggestions?

• Strip out the bottom bracket
  
• Put the frame upside down
  
• Pour in 1/2 litre of coca cola (full fat, regular stuff)
  
• Leave for a day or two
  
• Drain the coke out of the frame (put it the right way up)
  
• Pull the seat post out (it will still be tight, but it won't be bonded anymore)