A few days after i had posted my code on the Arduino forums back in early 2010, Mark S adapted it to be table driven. Since it is table driven it uses no RAM. While it complicates the sketch a bit it is a more efficient way of setting up the large font and goes a long way to making the fonts usable. I don't fully understand it myself but i'm including the code here in text form only.
This was made back in 2008 on IDE 0.8. Things have changed a bit since then so the sketch might not compile. I had to make some adjustments to my original sketch before i could post it here since the Liquid CrystalLibrary had changed a bit since i last used the sketch.
Here is a link to the thread in the Arduino Forum Archives where i first demonstrated this custom font. There you can read about the evolution that took place in refining the font and the sketch.